On those platforms, users could post seemingly anything, and if they've got good following they could get thousand or likes and hundreds of comments. Now, those are worth something on Hive not Instagram.
This isn't necessarily correct, they might not earn money from the Instagram company, but they can earn from sponsors, patrons, ko-fi, donations, commissions, ads etc.
Also it seems those creators who earn well on Hive, know how to use other social media and are probably earning something, just without a dollar value on each post.