Remember the book "GP and the Goblet of Fire" when Krum catches the snitch, but Bulgaria loses from lack of points. Someone even bet on this outcome
There is not always a victory from the capture of the snitch. There are games in the history of Quidditch that lasted more than one day and more than one week. Capturing the Snitch ends the game and gives the catcher team 150 points. So if the first team has 350 points, and the second has only 100, the second team will not win the snitch, because 350 is still more.
Because the Snitch doesn't appear right away. And in general, everything is connected with the fact that only catchers can chase the Snitch. Reread the chapter from Philosopher's Stone where Harry is just starting to play - there Oliver Wood explains everything competently.