He wont be the next Stanton because Stanton can play RF and Jiminez is going to be a LFer. If you want to argue that's nitpicking fine but there's a vast difference in value between a LF who can hit and a RF who can hit. Also while I know a lot of people love to shit on Schwarber for a rough 2 month stretch to start 2017, he hit .334/.432/.619 in the minors with 38 HRs in 158 games. Incidentally he's also hit 38 HRs in 176 games in the majors so that part of his game is already here though obviously hitting .215/.328/.451, the average hasn't come with it though to be fair his walk rate is actually better. As a comparison to Jiminez, he has hit .300/.349/.498 in the minors with 43 HRs in 296 games.
So, if you're asking for an answer to "why" it's really that simple. They believe in Schwarber more. That was the case in the Andrew Miller talks when they wouldn't touch him but gave up Torres for Chapman as well. And contrary to the belief some hold here, there's plenty of reason to buy into that logic not the least of which is what Schwarber has done to great pitching in the playoffs.
As for Quintana, his numbers look almost identical to what he did in 2014 which was his best season other than a slightly elevated walk rate but that has also come with a 10+ k/9 which is fantastic. If people want to jump ship that's their choice but I see no reason to believe he's changed from one of the most valuable pitchers in baseball the past 3 years and he's on a fantastic contract.