It’s exactly what he said (at 1:35)

https://youtu.be/RTtdWiKX5Ow

Cars. Need I say more?

Because modern web is bloatware. Too much javascript, CSS, ads and cookie popups. A phone’s hardware and internet speeds are generally not as fast as a desktop. So, it takes much longer to render on a phone.

Also, a lot websites nowadays deliberately make their mobile web experience shitty (cough ** reddit cough) to force their users to install their app.