Why are Memphis Grizzlies in the playoffs and Golden State Warriors are not even though Golden State Warriors have more victories? Why was the last game important if it's not the number of victories that matters?
For the 2020-21 season the NBA introduced a play-in tournament (somewhat similar to those we saw in 2019-20 post Covid shutdowns).
As part of these play-in games, the 7th and 8th seeds of each conference at the end of regular season played each other, where the winner would be ranked the 7th seed for the playoffs. The 9th and 10th ranked teams, would also play each other. The winner plays the loser of the 7th and 8th seed game and would be ranked as the 8th seed of the playoffs.
Here is a picture showing what I described above with more clarity:
In the play-ins, the Warriors finished the season 8th, and played the Lakers who finished 7th. Lakers won that match and clinched a playoff berth as the 7th seed.
Since the Warriors lost, they played the winner of 9th and 10th seed, which was the Memphis Grizzlies. So the Grizzlies and the Warriors played a single game elimination to enter the playoffs. Since the Grizzlies won, then entered the playoffs as the 8th seed, despite finishing 9th in the regular season.