When Luna/Terra collapse happened, it was extensively discussed on Hive. It didn't collapse because of 20% APR but rather due to lack of safeguards in place to protect the network and coins. Some say Luna's death spiral was inevitable and programmed to happen.
Hive has measures in place to prevent this. Blockchain have corrective measures when the HBD market cap goes higher than certain threshold compared to Hive market cap.
It is actually very interesting if you look deeper into how Luna's protocol worked and how Hive works. It is a longer topic though. Dalz had some interesting posts on the topic.
I agree that there's more deeper reasons behind Terra's collapse. Just like FTX. I fully trust HBD's APR offer, it's just that it's way too high from a business stand point. This could attract investors and bring new players in Hive ecosystem, but in the long run as I always say it's very difficult for a business to offer a fixed 20% return annually.