I think the frustration with Simmons went way far beyond what happened in his last playoffs, likely for longer than that season, even. So while I do think Embiid should keep his mouth shut in front of the media, as far as alienation goes, I suspect the way Simmons didn't work on his shortcomings, practiced, and maybe acted around his teammates, drove those feelings. Yeah, he got thrown under the bus at the end, but I think that was the culmination of a lot of things beyond those playoffs.
I think Simmons alienated his teammates long before those playoffs. As good as he was, those guys knew he could be so much better with a little more work, and probably got tired of babying and trying to coax that effort out of him.
So as much as I think Embiid is just naturally an asshole, I don't put too much blame on him for the Simmons situation. Other stuff, sure.