Everything in life has a purpose, and that's God's will. If you were able to go back in time and change something, then you go again God's will, not only that - but you overcome it, which is impossible.

I also see your points but being a satanist is not a proof of changing the timeline, the other 2 sentences are only theoretical.

My theory is that they use anything related to different timelines to convince people that your actions don't matter, if another timeline can do it differently, and God's decisions can be overruled by humans, if they can change the timeline.

The Mandela effect stands on very few examples that illogically lead to a grand conclusion. However, every parallel universe scenario leads to a paradox, not tiny changes in what people remember.

I agree that they are satanists, but even Satan couldn't get even half the angels to follow him... How can we then assume that he can overturn any of God's decisions?