It doesn’t make sense for him to not send Fujitora to fuck Luffy (Sabo at that point) up.
BM sent an army of hax users when luffy defeated Cracker. She knew a weakened Luffy is still a threat a bit.
He sent Cracker cause he knew he defeated Doffy
this is the only villain who didn't underestimate Luffy really.
He did say explicitly that he wasn’t underestimating Luffy and that he had more potential than Law… then proceeded to underestimate him lol