You are essentially arguing that we should never judge a manager's moves because there are too many factors at play and we don't know all of them. Respectfully, that's ridiculous.You've done this multiple times now, claiming that because a coach did something and the decision didn't work that the decision was clearly wrong, which is simply ridiculous. There's almost never a way to know if the decision was right or wrong because there are too many factors.
Part of the judgement is what goes into the decision, and part of it is what comes out of it. It's more than fair to judge a move if it doesn't work. This is a results-based business. Was it a mistake for Dave Roberts to pull Rich Hill in Game 4 in 2018? You bet your ass it was, because it didn't work. I'll go further: it was a mistake by Grady Little to leave Pedro in the game in Game 5 against OAK in 2003 even though they won the game.
It's never unfair to at least partially judge a move by its results.
The difference was that Cash pulled him after only the second hit, and at 73 pitches, after utterly dominating. It's one thing to pull him like they did in the first game after giving up 4 straight baserunners, but after one hit in the 6th? That was a massive overreaction on Cash' part.game 6 of the WS: Snell was dominating into the 6th, TB was winning 1-0. This time the 18th batter singled and Cash had already seen this film so he pulled him. Anderson blew it but Cash made the right decision in pulling Snell, just the wrong choice of relievers (Anderson was burnt by being overused in the playoffs).
This year Snell has perhaps the biggest Home/away pitching splits I've ever seen. Something odd is going on with him.