Honestly,

A) expand his audience

B) prove that Leftists can come on his show and it won't be internet blood sports, even if they lose

If the Leftists realize that they can come on and be treated with a modicum of respect (pro-lyncher Vaush being literally one of the worst among them), they might be willing to go to him more often.

Tim Pool is one of the few people out there who's had Feedom Toons, Project Veritas, and Vaush all on his show. That's a good array of interviews that few can really manage from a broad spectrum.