Wilder is signed with PBC, which has a multi year and multimillion dollar PPV deal with Fox Sports/InDemand. Joshua is signed with Matchroom, which has a huge contract to broadcast fights on DAZN (via a monthly subscription, not the traditional PPV model). There's always been issues in boxing with promoters getting in the way of making the fights happen, but the last few years, as networks and sub services have been desperate for content, those promoters are also signing deals with specific networks, which only complicates things further.