By making a post, I just wanted to see the whole history of all unpaid bounty, what is main reason and who is the cheater for not paid.
These are just studies, actually there are articles out there already telling most crowdsale in crypto are scam especially in ICO.
This one was published in 2018
https://www.investopedia.com/news/80-icos-are-scams-report/80% of ICOs Are Scams: Report
OP was telling 90% but its his just estimate maybe, because although a crowdsale is successful sometimes bounty hunters are not paid, so they have a lower success rate.
Now I can telling that bounty manager can't do it or check what is going on CEO brain. Most of the project failed because of development and most of the project paid to bounty hunters.
The call is on the CEO or team behind the project, and bounty managers and bounty hunters are just workers, they do what they are told to do with a specific reward, if the CEO scam, everyone will not get anything.