His fastball wasn’t working for him earlier so he switched to mostly breaking stuff. Berrios has made his career from his breaking pitches tunneling off his fastball. When his breaking stuff flattens out with non-effective velocity to turn to, you get those six ghoulish starts.
Last night and even the game before he’s seemed to get the quality back in that fastball and his breaking stuff was dancing. With a free swinging, not very good contact team in the Phillies you get a K performance like last night where his FIP was 1.05 I believe.
Those who like to speculate suggested him moving back to the middle of the pitching mound helped cure whatever was ailing him.
By the way me answering your question isn’t to imply “I’m smarter than you”, just providing insight on what I’ve seen with Berrios this season.