AITA for wanting a precise reason as to why my ex best friend ended our friendship?

So I (f19) got a text from my ex best friend (M21) today in which he told me that he wants to end our friendship. He kinda didn't talk to me for a while, but also never told me that he needed a bit of distance from me. Which first of all I kinda hated it. I don't have a problem if he needs time for himself, but like why couldn't he communicate that? Sorry I'm still a bit overwhelmed with the situation. Back on track he texted me today saying he wants to end our friendship of 8 years, since it's burdening his mental health. I texted him back saying that I can accept his decision, but asked how it's burdening his mental health, because I couldn't really place the statement. To that he responded calling me condescending and saying that's exactly the reason why? Really I'm just confused. I kinda want a set reason, as to why he wanted to end our friendship and the reasoning he gave me didn't really make sense to me, because nothing happened. Like we didn't have a fight, he never said anything in regards of being burdend by being friends with me or something similar. We also never really had problems with eachother. And I kinda can't understand his decision. Does that make me an AH?