I think it's a streak. He's going to finish the season at or below his career averages and negative WAR, won't he? The law of averages is undefeated. It's magic. He didn't suddenly become a superstar by moving 80 miles north. I doubt he woke up one day and said to himself, "I'd prefer to make $10 million dollars instead of 0 dollars -- I'm going to start trying at my job". Maybe a little bit, it was probably a wake up call, but at the end of the day, we've pretty much seen what kind of player he is...a pretty good player that can probably show a little more than what what we saw in Chicago. But he probably isn't an all-star or a top 50 hitter. He's done enough to have his option picked up, which is great. I'd take Pseudo-Vaughn over Rhys Hoskins at half the cost.
But it's 106 plate appearances with Milwaukee vs 2451 with us. It isn't really a sample size. He's facing an atypical amount of lefties. It's random. His stats were bound to average out and he seems to be in a really good environment for him. Watching him this year with us, it's not like he regressed. He looked the same. He was unlucky but pretty much the same guy. I'm not really watching the Brewers, but is he doing anything different? It might be a confidence/mental thing, but can that be sustained over the life of a post-arbitration contract?
We're seeing that 'deadline superstar' Eugenio Suarez is going to average out to a slightly above average hitter in line with his highly variable career averages, as such there's probably a reason he didn't net a huge return and why the Yankees didn't bother to give up anything for him and might've even preferred Ryan McMahon (who has been marginally better than Eugene, a whole 0.9 bWAR better since the trade).
These stats are very much influenced by minor perturbations, is there any actual reason to believe that Vaughn is a different player? To his credit, he's hitting a lot of bombs not in line with his career averages. Is there evidence to suggest he can sustain it? I think to myself: I've watched him play ball for several years, is he all of a sudden "that guy"? Is team chemistry infectious like it was when Texas won the World Series?
I suspect nobody really knows what they're talking about in this sport (besides the people at FutureSox, shout out, lucky us; J Gonzalez is budding star though), sometimes guys just get hot for extended periods. Part of the reason baseball is the best sport, these things are just mystical. There's no understanding it. The physicists and materialists say the fastball cannot possibly rise, that gravity doesn't work that way, meanwhile baseball legend Mookie Betts says, "get in the batter's box and see for yourself". I think it's a streak.