Fighters do not control their own schedules alone
A professional boxer typically signs with a promoter who arranges fights, negotiates purses and often controls broadcasting relationships, meaning the fighter's stated wish to face a particular opponent is only the beginning of a much longer negotiation. Two fighters can be entirely willing to fight each other while the surrounding business arrangements remain unresolved for months or years.
Where the friction comes from
When two fighters are signed to different promoters, or their fights are broadcast on competing platforms, arranging a bout means those organisations agreeing on money splits, venue, date and broadcast rights, none of which the fighters directly control. Rivalries between promotional companies, built up over years of competing for the same audience, can make this negotiation harder even when the fight would clearly be popular.
Why fans should watch the business, not just the ranking
Understanding this is useful because it explains why the most deserving matchup by ranking alone is often not the next fight to be made, and why a seemingly simple fight can take years to materialise. Once the business terms align, however, these fights tend to happen relatively quickly, which is why sudden announcements of long-awaited matchups often follow lengthy, publicly invisible negotiation.