That is not his responsibility.
So who is responsible?
To be honest I can't agree with this sentence. You don't think a managers should have minimum responsibility? I am agree if it's exit scam. No one can stop exit scammers , not important team how potential. But before start any project should search minimum. At least use Google search for picture.
And how do you define minimum responsibility? Using google search for the picture or reverse image matching doesn't count as 'minimum responsibility'.More than the managers it's responsibility of the participants to do all that knowing managers will get paid anyway but if the project turns out to be a scam, it's the bounty whores who'd suffer. I get it obvious stuff should be taken care of but usually these scammers are well spoken and professional with the managers. I wouldn't participate in a random bounty knowing if it turns out to be a scam, I wouldn't get paid but the manager would. Stop depending on spoon feeding.