Cleveland's lineup is very good. Maybe the Astros pitchers were just better.
The Indians had the 5th best record in the AL, coming out of arguably the weakest division (every other team was under .500). The Astros had the 2nd best record in the AL, coming out of arguably the toughest division (the worst team would not have been last in any other division, 4 of the 6 above .500).
So maybe their record was flattering while the Astros' was not. The 3-0 sweep was not expected, therefore, but not out of whack with how good the Astros are compared to most in the AL.
The Red Sox had the best record in the AL, but had the benefit of playing the Orioles 17 times from which they picked up 14 wins and 3 losses. Normalizing the Orioles to being just Rangers-bad probably takes 3 or 4 wins away from the Sox, but even then they'd still have a better record than the Astros (the Astros went 6-1 against the Orioles, so they'd lose wins too in a normalized count).
Of course, all of this is statistical nonsense. The Red Sox won 108 games and are very, very good. The Astros are very, very good too, and won 103 games. Head-to-head, it's 4-3 in favor of the Astros, including a 2-1 series in Boston in September in which the one home win required
a big assist from the HP ump.
Bottom line: I'm sure they're just as nervous as we are.