Nothing much? He is still averaging roughly the same amount of views as he always has. Hell, a video he released 2 weeks ago is already over 5m views.
This is definitely not an event he needed to "re-gain fame". This really is just what it is advertised as: a weird way to raise money for charity. I'm all for it, personally. Boxing is fun.
The funny thing is that many of the original content creators for these are actually on Twitch, not Youtube. The Youtube videos are made by what I consider leeches, that don't have skill to create content on their own, but have found they can make a modest living by making highlight videos of other actual streamer's content from Twitch, that they then post on Youtube. At some point really copyright laws I think will put a stop to that since it is 90% using other's content, but for now it's a grey area that they are able to get away with.
Worse yet since that's all the Youtube highlight video makers have, they work to try to find any comment or clip that could be interpreted as drama or shocking for views. So because of that, you have to take some of this drama or clashing with a grain of salt. Streamers themselves don't really gain Twitch viewers with drama, more the opposite. They try to avoid it. It's Youtubers wanting a clickbait highlight video title that are looking for the drama. It seems to work over there, but not so much on Twitch.