Why do some website logins have the username and password entry on different pages?

I need to load a second page to enter my password in some sites. Why is this? I even have a site I use that has the username, password and 2FA entries on separate pages that each need to be loaded one after the other.

My uneducated guess is that it makes it harder for bots, but I can't imagine it being that much of an impedance 🤷‍

Cheers!