The number of moves wasn't what made it short - they reached move 41 - but it was the time (just two and a half hours) and the number of moves that actually mattered (approximately 21-23) that made it short. After Ian Nepomniachtchi's 21st move, it was evident that the players had given up on the game, and with a couple of short thinks just to make sure that all the i's were dotted and t's crossed, the players hoovered up almost all of the pieces, then blitzed out another 10 moves to get to move 40. At that point they were allowed to offer draws, and did.
After their epic game 6, it's no surprise that today's game was considerably shorter and less energetic. That favored Magnus Carlsen, of course, as he got through another black game while maintaining his lead. Still, it was useful for the challenger as well, as Nepo must have been exhausted from the previous game, and a little separation from the pain of yesterday's loss may have helped his mood. It may also have been to his advantage to finish things early today, to have some added reserves in case Carlsen tries to grind him to death in game 8 as well.
That will take place on Sunday; for now, here's today's game, with my brief annotations.