Navalny saw exile as a betrayal of both his country and his ideas and convictions. I think he mentioned that an opposition that is staying outside of Russia would lose moral legitimacy in the eyes of Russians too, or something similar.
It would be a noble cause if it were true. You need to really think sinister thoughts to get a glimpse of what really transpired there.
Don't think noble causes. Think money, blackmail. When thinking of timing of his death think of what else was going on in the west at that time. Think Tucker/Putin interview.