I wouldn't go that far, but I would also not rule out this possibility. One example can be N.Korea's state hackers, for which all of us are enemies.
And even if it's not them, do you really expect the hackers be nice people who care about their victims?! Then they would notify the team, not steal people's money!
Some hackers are indeed doing that for the sake of finding loopholes on security. There are some cases, such as some funds or corresponding money have been returned to the project in exchange of bounty. Like on Optimism and nomad. Not sure to others, maybe it depends on the hacker's goal.
But I believe some didnt only doing that for money cause if its then they are reallt brutal people.