What was this...?

Okay, so I'm kind of reposting from another site but I'm trying to make sense of this incident...

Basically, I was leaving campus. Already stopped at the curb was the bus I take to get home. Now, it's a route that leaves at pretty regular intervals so if I miss one chance, I only need to wait about 15 for another bus and it's not a huge deal.

So this bus is at the curb and a couple people are still getting on. Lady in a wheelchair boards, so they've got a ramp lowered. And by the time I'm up to the bus, everyone's just gotten on the bus and I still see a couple people finding seats (and the bus doesn't look that crowded- still what looks like a couple totally empty seats here and there).

But as soon as I'm about to step on, the bus doors close and it starts driving off. I signal to the driver, kind of wave to him to see if he'll stop. He doesn't. I follow after it a couple paces- doesn't stop.

Now, before I was passing 100% and looked significantly more female, I'd had similar incidents. The bus would drive off as I was coming out, but it'd stop as soon as the guy noticed me.

...So, what was this? Was this particular driver just an asshole? I mean, I kind of have a sinking feeling he would've stopped for a female or a cisguy. It's pretty obvious I'm trans- I notice people start getting pretty uncomfortable around me once I speak...