But people leaving because controversial decisions always happen. If Tera had been banned or if sleep clause had been maintained the same number of people would have left just for different reasons. I think we should listen to people who keep playing instead of people who can leave if something they don't approve happen because they can leave again.
If someone only played the tier until the Tera decision there is no guarantee they will enjoy and continue to play OU even if it's banned.
Well, this could be a self fulfilling prophecy by the same logic. If we banned Tera and the same number of folks left for that, then the people left behind could be more anti-Tera crowd and so on. And so the point that not banning Tera left more pro-Tera people behind and generated a cycle of increasing pro-Tera majority would likely be getting at that. You stayed. You claim you are more invested/more informed. Just maybe other folks would have stayed and claimed to be more invested/informed with different decisions. Does that make them worse? Not necesarrily.
Personally, I don't believe in this because Tera is just a more popular mechanic. So I believe more people support Tera in general, and in some cases, regardless of how healthy it is for the tier. But in other cases, I'm sure there are plenty of folks who genuinely believe it isn't so bad. As an anti-Tera person myself, by technicality, I don't like that term because I don't hate Tera. I think it's a fun mechanic. Just poorly balanced and not good for the game.
I will say that I have been in and out of the tier myself because gen 9 power creep with Tera is just frustrating sometimes. I did miss the last survey where Tera was on it. So I don't know how many other people there are like me. But it's not necesarrily an invalid point to say that folks may be less engaged because of the direction of the tier. It's also too black and white to say folks left when some have probably been in and out or what have you. Sometimes, there are those in the Smogon community who tend to too easily dismiss the opinion of others because of arbitrary reasons.
However, I will reiterate that I do get the sense Tera is generally more popular. So in this case, I tend to doubt there would be enough folks who have been semi-invested or irregularly invested to make a difference. I guess it also depends on how close the votes are, but I'm guessing probably not.