Totally forgot of Ulti’s relationship with Kaido lol, that should have been in manga. The other F6, calamities, and most of his crew still think too highly of Kaido or either fear him. That would put up a wall more so than what I’d imagine BM and Kaido’s more casual relationship could be.
They also go way back and probably shared the same ideals, he had that excited and carefree nature the first time he met King. And now he’s sad and drunk most of the time lol, his time with Rocks was the nostalgic glory days for him.