why wasn't this a draw

This should've been a draw, no? I lost by timeout.

This was played on Lichess so it may have different draw rules on timeout.
Also, in hindsight, 58...Rxc4 was really stupid, but i had about 8 seconds left and I thought it would be a draw.

Under FIDE regulations if mate is possible by any series of legal moves by the side with time then they win. With that material, mate is possible. Lichess apparently uses the FIDE rules.

Here it would be a draw

Hmmm.. that sucks — thank you, though.

As inconvenient as this is, it prevents people from stalling so they can get a draw in extremely specific positions where a single knight or bishop actually can inevitably checkmate, such as here:

If black were to stall to timeout instead of playing a2, it would be a draw on this website, even though the position is mate in one.

For this reason, I think that "insufficient material" rules should be put on hold if the evaluation shows a forced checkmate. But if there's no way to forcibly win, then it's a draw. That would be much more convenient, though I imagine it'd be almost impossible to program.

It doesn't sound difficult to program at all. 
If the evaluation shows a mate in the near future, then it's a win, not a draw.
If it doesn't, it's a draw.

It would be like three lines of code.

Although I don't know if SF can be running during a match to get the eval.