First man to win the Ring cruiserweight and heavyweight titles and the second man since Evander Holyfield to win the lineal cruiserweight and heavyweight titles. Also made AJ have a mental breakdown. Absolute legend.
He didn’t win the lineal heavyweight title. How can he win that off Joshua when Fury holds that recognition?
If Usyk lost to someone (who is not named Fury), that someone also became the lineal champion, and Fury did not retire; in that case, Usyk would really make history (historical absurdity). The concept of "the man who beat the man" would disappear.
Fury retired his claim to being champion. Many champions have retired and come back, especially when they go out on top.
If Fury is the lineal champ, then he must be the lineal champ until infinity. If he can take the title into retirement with him, then what can lift the title off of him? Nothing.