It makes zero sense for all of those bosses to take off running the way they did. What if they had stayed put? What could the police really do about a bunch of friends getting together at a backyard BBQ? It seems to me that the arrests and raid wouldn't have happened if not for them scurrying in all directions like cockroaches. I believe that Mafia history would have turned out differently if they had just carried on with their function and let the police watch, like who cares?

Warrants

It was stupid of them to run, I agree they should have just stayed put and it would not have been as big a deal as it turned out to be. Them running made it look 100 times worse. I think a few panicked and ran, and the rest decided they would run too. Running was a big screw up.

It makes me ask this: Did anyone just stay put and sit as if nothing was wrong?

I think there were a couple things at play.
(1) the natural propensity of these guys to keep everything secret.
(2) The possibility that some of them were legally prohibited from consorting with known felons.
(3) The fact that those arrested were carrying the modern-day equivalent of over 3 1/2 million dollars.
(4) The possibility that the attendees thought they were the target of a long term,well planned Govt. raid as opposed to Croswell's relatively quick operation.
The main motivation seems to be keeping the existence of a National Syndicate a secret, but ironically,the raid shone the spotlight on it.
At the time,the police only had suspicion of illegal activity,and had no legal grounds whatsoever to search the house.

Spot on

The problema was that the meeting was held in the middle of nowhere where all those people made the police of a sleepy city suspicious.
If they had it in las vegas, miami or in any big city and had bribed the police properly, the meeting would have taken place without problems.

They still didn't have to run, it was so amateurish. They behaved like small-scale street crooks, not the cream of the crop of America's underworld.