Draw by insufficient material

Hello everyone,

I''ve encountered a strange issue in which the game ended in a draw because of insufficient material (I was the one having insufficient material (only king), while my opponent had a queen and a bishop) instead of me winning since my opponent ran out of time. As far as I've read, it would have also been a draw if I was the one running out of time. My question is: why is this happening? Is there a motivation behind this? I'd be really interested to hear it out .

Black ran out of time. However, White didn't have a way to checkmate, so it's a draw. (Otherwise Black would have lost.)

It does make sense in my case. However, I think I read somewhere that it would have also been a draw if I ran out of time, is that right? If yes, why is that? Also, if I had a bishop a king, which cannot checkmate, would that have also qualified as a draw by insufficient material? 

So why was this game I played a couple of months ago ruled as a draw?

https://www.chess.com/live/game/3214395541

White can achieve a checkmate, so this should have been a win for me, right?

You can't checkmate with just a bishop as far as I know.