There apparently never really ware that many paying customers using Helium's network, so the payouts ware comming from people paying the data credit fees to have their miner listed and accepted to the network. The moment the network stops expanding, the demand for HNT to pay for datacredits will be gone.

https://cointelegraph.com/news/critique-on-helium-s-6-5k-mon...

And now that seems to have happened.