I think it's partly this guy's fault for being a doormat. A list of all the things he did for her:
He would always offer a helping hand, or would listen. We'd have conversations on skype, and he'd always be supportive and offer friendly advice. At work, he was really flexible with his shifts and would always rearrange to cover mine. For example, if I couldn't make a shift on a certain day, and would prefer another day, he would always gladly swap with me. He was always friendly about it. When I was moving apartments a couple months ago, he helped me move my stuff. When I didn't have my car for about two weeks, he drove me to work and home every day. He was an incredibly good friend and I was really thankful to have someone like him around.
And he was also incredibly emotionally supportive, whenever I'd talk about my issues with friends or family, he'd listen. I've had depression and anxiety in the past, I take meds for it, and it comes back every now and again. I have a lot of personal worries, fears and issues, and he's always ready to listen and be supportive.
He asks her out and of course she says no. Surprisingly he doesn't just become an orbiter and keep doing nice things for her, instead he moves on which annoys her:
Then over the next few days I noticed things were a bit different. He would still talk to me, chit chat occasionally, smile, say Hi. But he wasn't as receptive to conversations with me any more. On skype when we'd talk, he'd take longer to respond, and seems always uninterested and giving one word responses. With work, he's no longer swapping any shifts with me. He says he can't manage the time, and he's also on a busy work and life schedule that he can't always move things around.
I'm moving apartments again in a months time, and I asked if he'd be ready to help me move again like last time, he said probably not and that he's too busy.
He's not giving her undivided attention and doing her favors all the time so what's her reaction?
Now suddenly, its almost like he's an asshole.
Did I make friends with a "nice guy"? Was he really just an asshole all along only pretending to be nice to get in my pants?
Lesson: So if a guy doesn't give you undivided attention and time, he's an asshole.
Yeah, you knew him for 8 months OP. He was never really your "friend" as he viewed you as a potential love interest. You shut him now, now he's protecting himself by creating distance and finding other girls to prioritize for dating.
You are not entitled to preferential treatment. You are not dating him. You are not sleeping with him. He's just a dude and now he has other priorities. You don't get the benefit of boyfriend-like behavior from someone you will only accept platonic friendship with.
So, no he isn't an asshole. He's just a dude with healthy boundaries.