If there's already an EMT managing the situation first aiders are usually told to step back and let them deal with it. If they ignore that advice then, yeah, they're idiots.

Also hard to do CPR without hurting someone. Bad bruising at the very minimum, more likely a few cracked ribs. I talked to a corpsman in the Irish navy once and he said he performed CPR on 10 people, none of them recovered. It's a bit of a hail mary.

He did say a colleague of his had brought someone back at the airport though.