I'll give a counterpoint.
After the Bruins formed the core of their leadership group around Chara and Bergeron, they had several high profile acrimonious exits in the following seasons. First it was Kessel, and then it was Seguin, and then Hamilton. When the leadership sets the tone, some players don't follow and have to find new homes.
I really don't think Tarasov is central to this. I think it's a distrust of Elvis, largely to do with off-ice factors, that has been brewing for years. They don't want him in the room. I think the decision to move on when they can from Elvis was made a long time ago, there's no need for a trade request, they're already trying. That they're trying to trade him is perhaps why he's been sitting lately, because they don't want an injury or bad start to derail a deal that is very close.
I guess my comments are the same as I made above. This goes way further back, to Matiss and Manny, and also to the very bad year last year.
Elvis has played like a #1 goalie this year. I don't think there's any on-ice problem with him this year.