I respect usyks position. He's thinking long game. What exactly is in it for him?
If he allows aj to fight fury anyway, there's a rematch clause meaning he wouldn't get the winner until after the second fight anyway. So he would fight for a vacant title later rather than just fighting for it next by forcing aj to vacate. Lets look at the timelines
Scenario 1: usyk takes step aside money
May 2021 :
fury v aj1
Usyk vs random opponent (possibly)
September 2021 (wbo vacated) :
fury v aj2
Usyk vs xxx for vacant title
March 2022:
Usyk vs aj/fury (potentially)
Scenario 2: usyk doesn't step aside
May 2021 :
Fury v aj1
Usyk vs xxx for vacant title
September 2021:
Fury vs aj2
Usyk title defence
March 2022:
Usyk vs aj/fury
In scenario 2,he potentially gets an extra fight in, unless he takes another fight first and risks losing his position as mandatory. The additional fight under scenario 2 would be usyk as wbo champion. He is no better off taking step aside other than an extra million (which he would probably make up in the additional fight). He is no closer to the big aj/fury fight under scenario 1. At least with scenario 2 he has more control over his own destiny and goes into a potential aj/fury fight in a stronger position