Flat Earthers hold their belief because they know something's off about the official narrative and it's the closest they've gotten to the truth. It's the most stigmatized and ridiculed theory, not because they believe in a flat earth, but rather the other truths many have uncovered along the way.
(media.communities.win)
Speculation
Flat earthers don't believe what you are showing here. There is no evidence that these other "planets" exist other than Nasa cartoons. If you look for yourself through a telescope all you can see is a circular light.
Many people actually do believe in flat earth because it makes more sense.
This is a just a meme that is commonly used by those who ridicule flat earthers due to the stigma created around it. I have a fairly good idea of many of their beliefs. I did look at some of their primary arguments at one point.
I'm not saying they are wrong to believe that either. Regardless of whether or not the earth is actually flat, the official narrative is almost certainly a lie, so anything is possible.
Fair enough! This is a reasonable position.