Lemmy.world allows creating communities, where as lemmy.ml doesn't. For me that was a big reason why I moved from lemmy.ml to lemmy.world. (I made this account after beehaw defederated lemmy.world. I would have made this my default account, but sadly there still seems to be some communication issues between instances. I have some communities on lemmy.world, but I don't see the content sync properly here.)
From what I recall (from all of 8 days ago) Beehaw said it was because lemmy.world allowed unrestricted signups and therefore was at risk from bots or (i guess) unsavory people, while Beehaw was trying to have a curated membership to be 'safe'.
It seems somewhat lame or maybe insulting, but on the other hand not every site has to have the same philosophy. Lemmy is essentially forum software and instances don't have to be federated with any others if they don't want to be. If someone wanted they could start their own standalone site for Washington Park Roller Skating Club or whatever they want and that would be a fine use of the software.
Their stated reason being that currently they don't feel like they have the moderation tools to remove rule breaking content should a bunch of bots and spammers flood in
I feel like that's reasonable. Lemmy is still in very active development, and still building up a lot of features. Also, their defederation isn't meant to be permanent either
I wouldn't call them douchey. It's not like they're causing damage to anybody else and there's nothing wrong with using their own lemmy instance as a local bbs.
That said, I decided not to join them when I saw I would have to go through a sort of interview process explaining how I would contribute to them. They also have a long winded text to say the rules will be applied arbitrarily.
Fully unrestricted Lemmy.world didn't use captcha or require an email. Beehaw could ban someone and in seconds troll_2 would have a new account and pick back up.
It's temporary until there are better mod tools - beehaw is supposed to be a safe space but they cannot keep their promise when federating with everyone else due to the amount of posts.