if he has the key he could buy security (move the money to a multisig, etc)
if he doesn't have the key then of course he's motivated to make sure bad people don't think otherwise (but the usual thing about bad people is they don't really have a habit of giving up without a fight, so if someone really thinks he has the keys he cannot do shit to convince them otherwise, so he's again back to hiring security)
if he has the key he could buy security (move the money to a multisig, etc)
if he doesn't have the key then of course he's motivated to make sure bad people don't think otherwise (but the usual thing about bad people is they don't really have a habit of giving up without a fight, so if someone really thinks he has the keys he cannot do shit to convince them otherwise, so he's again back to hiring security)