All evidence suggests massive climate change took place in Egypt and the Sahara.

Not so massive. Massive climate change are ice ages and their endings.

Yes, Nile delta and higher was pretty green at the time, that is why people settled there. Such changes are not rare, Greenland was once green, and crocodiles lived in Volga river. Unless CO2 levels will rise to normal levels (around 1000ppm), climate will not be stable.

Except that they are a phenomenon not explained with bronze tools.

To cut limestone and sandstone you don't need even bronze. You need a rope, some glue and sand. Soak rope in glue, then cover it with sand and you will have pretty precision cutter for soft stones. This will give more than decent cut, due to self-aligning of the rope to shortest distance between ends. Then, ypou could polish cut surface with a plank, sand and some water. With enough workforce and time, you don't need magic tools to make Egypt pyramids.

I have megalitic construction in nearest town - it is a huge rampart with a kremlin wall on it. It has larger footprint than Cheops pyramid, and at least comparable to it in terms of mass that was moved by humans. And no, thousand years ago, when that construction was build people didn't have excavators, bulldozers, cranes and other modern machinery. And hardly their tools was fundamentally different from Egyptian ones. It is fascinating, what people did in ancient times, but there is no any miracle, just amount of workforce and time.

I spent a lot of time trying to find any sign of some hidden ancient knowledge in pyramids, but there are none I could detect, not even talking about using. I even build a small pyramid once, scaled copy of Cheops. :) Had some fun, but nothing more. Knives did not sharpen inside pyramid, water did not stay fresh longer, no any energy anomalies or whatever. Of course it was from regular bricks, bought for the house facing, not from limestone, but pyramid apologists insist that the thing is in shape not in the material. May be you are aware, near Moscow one rich man (Alexander Golod) even build a pyramid 44 meters in height. He was well into all that ancient knowledge stuff, and built dozens of pyramids around country. AFAIK he have contacts and projects with John DeSalvo. All in all there is nothing except entertainment happens in pyramids.

What were they trying to say? Why did they believe what they did, placing into alignment structures that heralded the stars?

All that time counting thing using space objects was very important for ancient people. They literally depended on it in the absense of a decent calendar carefully synced with Earth orbit. When to sow the wheat? When fertilize fruit trees? It was literally a "life or death" question. So they truly believed that stars influence or even rule their lives. That's why a lot of attention to the skies.

The question of human origin could be even more weird than anyone think. God's creation, aliens, monkeys, ancient civilisations and so on, It could be even a weird combination of all that stuff. :) Ancient civilization created by God on another, more pleasant planet was eventually expelled to the Earth, and in order to survive in new environment they had to borrow some DNA sequences from local primates. :) That's why we have up to 10% of our DNA from unknown origin, switch to 30 hour activity cycle when not exposed to daylight and have that story about Eden in Bible.

All evidence suggests massive climate change took place in Egypt and the Sahara.

Not so massive. Massive climate change are ice ages and their endings.

Yes, Nile delta and higher was pretty green at the time, that is why people settled there. Such changes are not rare, Greenland was once green, and crocodiles lived in Volga river. Unless CO2 levels will rise to normal levels (around 1000ppm), climate will not be stable.

Except that they are a phenomenon not explained with bronze tools.

To cut limestone and sandstone you don't need even bronze. You need a rope, some glue and sand. Soak rope in glue, then cover it with sand and you will have pretty precision cutter for soft stones. This will give more than decent cut, due to self-aligning of the rope to shortest distance between ends. Then, ypou could polish cut surface with a plank, sand and some water. With enough workforce and time, you don't need magic tools to make Egypt pyramids.

I have megalitic construction in nearest town - it is a huge rampart with a kremlin wall on it. It has larger footprint than Cheops pyramid, and at least comparable to it in terms of mass that was moved by humans. And no, thousand years ago, when that construction was build people didn't have excavators, bulldozers, cranes and other modern machinery. And hardly their tools was fundamentally different from Egyptian ones. It is fascinating, what people did in ancient times, but there is no any miracle, just amount of workforce and time.

I spent a lot of time trying to find any sign of some hidden ancient knowledge in pyramids, but there are none I could detect, not even talking about using. I even build a small pyramid once, scaled copy of Cheops. :) Had some fun, but nothing more. Knives did not sharpen inside pyramid, water did not stay fresh longer, no any energy anomalies or whatever. Of course it was from regular bricks, not from limestone, but pyramid apologists insist that the thing is in shape not in the material. May be you are aware, near Moscow one rich man (Alexander Golod) even build a pyramid 44 meters in height. He was well into all that ancient knowledge stuff, and built dozens of pyramids around country. AFAIK he have contacts and projects with John DeSalvo. All in all there is nothing except entertainment happens in pyramids.

What were they trying to say? Why did they believe what they did, placing into alignment structures that heralded the stars?

All that time counting thing using space objects was very important for ancient people. They literally depended on it in the absense of a decent calendar carefully synced with Earth orbit. When to sow the wheat? When fertilize fruit trees? It was literally a "life or death" question. So they truly believed that stars influence or even rule their lives. That's why a lot of attention to the skies.

The question of human origin could be even more weird than anyone think. God's creation, aliens, monkeys, ancient civilisations and so on, It could be even a weird combination of all that stuff. :) Ancient civilization created by God on another, more pleasant planet was eventually expelled to the Earth, and in order to survive in new environment they had to borrow some DNA sequences from local primates. :) That's why we have up to 10% of our DNA from unknown origin, switch to 30 hour activity cycle when not exposed to daylight and have that story about Eden in Bible.