I started using zoom because my uni uses it. The setup to log in with your uni account was super easy, and it imported everyone else at the uni into your contacts. You can join a class or conference easily, you can start up a one-on-one meeting with your professor easily, etc. I don't know what the behind the scenes arrangements were, but Skype clearly didn't manage to fill that void.

It's so spread out anyway. I use zoom for uni, WhatsApp video call for casual hanging out with friends, Discord for internet friends and gaming, and Skype only for older relatives. Idk, at this point I feel like Skype's main user base is older people in my immigrant community - they got used to it when it was the only option to contact family abroad for free and they're not about to learn a second option.