Apparently Kimbrell was tipping his pitches all offseason until game 5 of the ALDS (with Eric Gagne of all people being the one that told Cora). That certainly explains why both the Yankees and Astros were teeing off on him, and why he did better in game 5
Figuring that out doesn't exactly fill me with confidence, though, since he could have been tipping pitches in multiple ways and we just caught the one