They leaved because they were tired and frustrated about everything in bounty. Where the much better place of opportunity they come and leave the other.
Haha, I agree, the hunters were usually very eager and enthusiastic at first to get their first rewards, like FOMO, they participate in every bounty campaign of every project they find out. Then when bounty campaigns take them too much effort and time, and some or the majority of the campaigns don't do them any good, they become discouraged and limited in bounty campaigns. They didn't even participate in any other bounty campaigns.
Then when a new wave appeared, the market entered the up-trend, many new projects appeared, many made profits, the hunters returned and got FOMO

Experience of 1 hunter ^^