Because engine chess is not human chess. Defending a position with a ~3300 ELO computer is not the same as doing it as a human down on the clock. Look up some of Mikhail Tal's games to see how you can become the best in the world whilst still playing moves that are "refuted" by engines.

Still he's heavily favoured in the tiebreaks, so I don't necessarily fault his strategy.

Leela is an inferior chess engine, and Leela and Stockfish were given equal time. In the human match, Carlsen and Caruana are closely matched and Carlsen had a significant clock advantage.

The engines are playing out the position here: https://www.chess.com/computer-chess-championship