The person who asks the question needs to mark the answer as accepted
At the moment it is up to the person asking the question to mark an answer as accepted. This will also trigger the payout of the bounty.
I noticed that a lot of times people won’t come back and review answers, which makes bounties stuck. I am considering adding a time component to it - after some period of inactivity on the question auto accept answer with most votes that has reached certain vote threshold. This is just an idea for now. Would love to hear what community thinks about it.