Last season, individual errors and sheer misfortune caused them to go out in the group stage, but they bounced back in the Europa League, advancing to the semis. In other words, they were disappointing in Europe, but not atrocious. More telling than the results was the way they played. Conte often had them wound tighter than a drum. In Serie A, where there was an evident gap in talent, it was the right approach: opponents were blown away by their intensity early on and they could manage games.
In Europe, however, opponents seemed to absorb Juve's intensity, leading them to get more frustrated and, perhaps, fearing failure. Engaging in this sort of pop psychology -- particularly when you're not in the dressing room -- is tricky and prone to misreads. But that's the impression you're left with when you compare, say, the Europa League semifinal against Benfica last season (or the away trip against Atletico Madrid in the group stage this year, when they were still in "Conte mode") and the two legs against Borussia Dortmund this year.
Those Juve teams tried to outwork and outwill the opposition, and when it didn't work, nerves quickly became frayed. This Juve team seems more accomplished, more self-assured, more confident that it can outplay the opposition without needing to turn it into some kind of epic battle of wits.