McLaren did win. Norris did not. F1 is a team sport. The drivers championship is secondary as it doesn’t award money or affect wind tunnel time.
Which brings us back to Checo. There's a strong argument to be made that he, driving the dominant car for the first six races and probably second best car for the remainder of the season, should have been able to score enough points to keep McLaren from winning the constructor's championship. He did not and Red Bull cut him loose at the end of last season.
The second seat at Red Bull has been a brutal spot to be in since Verstappen came along. Arguably their car is very tailored to his preferences, and it's hard for another driver to get the most out of it, or even set it up to suit their preferences. Whatever the case, it's been a bit of a revolving door.