I guess I still don't know why they thought he was dead. It was probably crappy that he never contacted them(we know why though) but I don't think Xavier's action rise to the level of just intentionally letting his students believe he was dead. At best they should have just had some doubt instead of definitely thinking he was deceased..
At the end of the day the X-men are grown ass adults. Xavier said his goodbyes and wanted them to lead better lives and did his best to ensure they could. They weren't entitled to anything else so I really just did not like the way Scott dumped all over him. The Xavier hate was just in too much overdrive which is probably why it bothers me so much. But to be fair, I don't think Scott was mad at him because he thought Xavier let him, believe he was dead. Just that he didn't give him the "choice" to stay active in mutant affairs, which still feels silly to me. Your father figure wanted to unburden you from leadership so you could go be happy with your family and you throw that back in his face as though it was some heinous act? Ridiculous.