Team success isn't how you judge a 1 for 1 trade lol so this is f***ing nonsense.
Mika Zibanejad had the best years of his career here, years that were way more productive and impactful than anything Brassard has ever done anywhere. Brass's production pretty much started to decline the second the Rangers moved him, they cut bait at the perfect time.
But even going by your logic, if the Rangers were to trade Zibanejad and then win the cup with whom ever they get back in that trade, would they indirectly win the Brass trade again? Because they wouldn't get player x had they kept Brassard (See how ridiculous this is?)