Gadol, it needs to be very clear that rav moshe did NOT say the slippery slope thing about the eruv. He held it is assur medeoraysoh, and has no tzad heter whatsoever. And the vast majority of poskim backed him on it. Some were on the fence but joined the prohibition to show solidarity.
And after rav moshe was niftar….people made the eruv. It was a chutzpah norah.