It was cancelled because of the lack of sales.
People might not be that dumb to spend a dime on an exhibition match between a professional boxer and a YouTuber who only wants to earn without being at the level of the passion that a professional figther has been in their entire life. IMHO, that's just a straight disrespectful to the boxing industry and for the aspiring future boxers. If you want to become a fighter, then you should start at the bottom.

Now, we all know this fight between Pacquiao and Mayweather for the rematch as been long awaited for the boxing fans. So they switch up to this contingency plan to earn millions of dollars. Pacquiao fight always sells as much as Mayweather. If you put this two in the same ring again, it's very possible to break the last sales they made from the first fight.