He just finds it very peaceful and thrilling. "Just him and the climb" kind of language.
Also I suppose clout has to be involved: only person to free solo El Capitan, as far as I know the only person to climb Taipei 101 let alone free solo (did the spiderman guy ever make it or was he arrested?)
For a deeper dive, the book "Alone on the wall" is a good read and I recommend it. https://www.goodreads.com/book/show/36531127-alone-on-the-wa..., although that said the book might be less appealing to someone who 'knows nothing about climbing' and is more of a time investment than the short documentary :)
But it's certainly time we admit everyone feels feelings diferently. Even something basal like pain experience is hugely individual with large variation.
(I get that there are more motivations underneath free soloing in general, but I doubt Taipei 101 with a million cameras is the climb he'd choose if it were not for the money.)
Your average roped climbers at a crag might get 3 pitches of climbing in an hour (sometimes even less when they're on hard stuff where they flail). You can get that done in 15 minutes free soloing. After climbing for a while there's a lot of terrain where you know the odds of falling are minuscule, and you know exactly when you feel insecure and have the option of backing off by down climbing. It's a very common practice among alpinists, where moving fast is an enormous advantage and the terrain usually isn't difficult compared to current sport climbing standards.