Pretty much ended when Phil Hartman (RIP) left.
In the early 90s they had: Phil Hartman, Mike Myers, David Spade, Adam Sandler, Chris Farley, Rob Schneider, Chris Rock.
Look how many of those had success outside of SNL. Notice that none of them are noted for being hardcore Leftists? Even if they vote liberal, they do not let their politics infect their comedy and they generally keep their mouths shut and do not show contempt for half the audience. Notice how different that is to the people who have been on since the mid 90s.