I have no doubt that there are many people who actually believe the earth is flat but honestly I feel like most of the people who make those posts and join those forums are just having some fun. At least I sincerely hope so because if not, that's downright frightening.

Maybe a littel of both adn one or the other all mixed up together.

I personally suspect the latter.

who knows apart from them?

There are three different types of Flat Earthers. First, there is the original FEs who believe the Earth is flat because of their religious beliefs. Then, there are these new age FEs that don't realize that their belief in a flat Earth stems from religious beliefs. Finally, there are the FE trolls that prob. don't actually believe the Earth is flat, but love to stir the shit pot.

Yes and yes...lol.

I honestly don't know. It seems unfathomable that anyone could ignore the data and the relatively simple examples that show a spherical Earth, but I've underestimated human stupidity in the past so I can't rule anything out.

Ignore the first type because nothing you can say will change their minds (well, you could try buying them a round-the-world trip). Ignore the second type because that's the only way to deal with attention-seekers (or you could buy them a one-way ticket to somewhere far away).

Yes and No.

Its the lack of formal fundamental education that they fall for that