They knew they weren't tourists. They applied for a tourist visa in lieu of the proper visa. They may not have been aware of the consequences but they were aware that their actions didn't represent their actual intent. If I visit Canada and steal socks from a department store, I might not be aware of the penalty, but I am aware of the crime.

ESTA is not a tourist visa. It's is a visa waiver program with somewhat limited business related entitlements.

They didn't apply for a tourist visa. I repeat, they didn't apply for a tourist visa.

If I cross into gang territory I might get shot. It's their turf and perhaps I should research the area to stay safe. That is my personal responsibility to stay safe. But that in no way would take any blame away from the gang members shooting me. In the same way these tourists are at fault, but perhaps there are lessons for US border security too? I'm sure tourist dollars are worth something to the US economy. It might be worth nurturing the tourist experience, to coax more people into the US.

Actually, they never said it's "in lieu of proper visa". It may be, but that's not what they wrote.

The only indication about any work may be the "colleagues-not-to-be", but that may well be just a description related for the J-1 process, not their later situation. If they already had friends in the US, what's wrong with deciding to just visit them anyway on the visa waiver? (and not going to work)