For sure that the developers have earned a lot specially with those tasks that are requiring to transact with any amount because they get a commission from the transfer fees. Think of it, millions of users were able to transact and even if they get a penny out of each transaction, they're all rich now. That's why the momentum was gone and participants have realized it quickly that they're being fooled around by these developers just for the sake points but in the end when the distribution is ready, they're not able to make it or just got very little and conclude that it's not worth it.
Plus, they were getting them to watch videos as well, think of how many videos they were watching a day, which meant that they were making a lot of money. With the tap to earn places, like Hamster Kombat, one of the biggest tasks were watching youtube videos every single day, mostly even multiple ones, even if they made 1 cent, or even less, per video watched, they had millions of people watching many videos per day, so they had the power of 50+ million views per day, and that should have made them a lot of money.
How do you think they were capable of paying 20+ dollars per user? They did so by earning from that, they didn't even get funding that much, they were just making money from that, so it's true that they had multiple ways of making money.