My best guess is he started feeling some time pressure and really wanted to trade for a clear draw, but crucially miscalculated the tempo and position of the K

My best guess is he started feeling some time pressure and really wanted to trade for a clear draw, but crucially miscalculated the tempo and position of the K vs KP ending. I'm not a grandmaster though, so I can only vaguely speculate since that's how I would have lost :)