My theory about why they are making more FLCL is due to low show availability. They are being locked out of newer, fresher shows (ex: They got Demon Slayer Season 1, but not season 2; They got the first 5 parts of Jojo, but not Stone Ocean) by being outbid by...really everyone. So they need to get content by making content. That is why they have embarked on a huge original series push lately (Uzumaki, Fena, Shenmue, Blade Runner: Black Lotus, 4 different FLCL sequels, Housing Complex C, and probably more in the future). The ones that have aired so far really haven't had a great reception, and the ratings aren't doing well, but they have to keep making more because they wouldn't have anything to air.
The other option (which they have exercised to a degree) is getting older shows. In 2020, they reaired Paranoia Agent, in 2018, they reaired the original FLCL, hell they even brought back One Piece for its third stint on the block! Not to mention Cowboy Bebop is back on the block as well. Also, the current block has somewhat old shows in Assassination Classroom and Made in Abyss which have seen a positivie reaction on the block.
Tl;dr Toonami is fucked unless Crunchyroll and every other streaming service on Earth simultaneously collapse in on themselves like neutron stars (which isn't going to happen)