Won the game but got only a 1/2 point

One of the players in the tournament had won his game convincingly with time still left on both ends of the clock. It was a clear checkmate but after the checkmate, he was awarded only 1/2 a point.

Here is the link to that game.


Though the game itself says '1-0'
On the Points table it shows '1/2'

Given below is the points table for the player 'tsupreeth'
lichess.org/swiss/ZickRp5t

He finished 12th in this tournament.

It must have been a bug. No other explanation. He got raiting points for a 1-0 result, but lichess said 1/2 in the tournament. Don't understand. Maybe he can complain to lichess, but i don't think that will help.