Medvedev played well in part because De Minaur allowed him to play well. Demon has less power than either Fritz or Sinner. His inability to overpower Medvedev means that Medvedev is freer to apply his finesse-based strategies, play cat-and-mouse games, and take control of points with power himself on occasion. It's a good matchup for Medvedev.
As I watched some highlights of Med vs. Demon, I was reminded of Mecir's matchups with Lendl and Wilander. Not that Med is a clone of Mecir by any means, but there are some similarities in their baseline approaches and their overall strengths and vulnerabilities. Mecir was very strong against Wilander -- had a winning H2H and absolutely destroyed Mats on a few occasions. But the Big Cat was generally ineffective against Lendl -- beat him once (at the Lipton, in one of Mecir's best-ever performances), but otherwise lost handily, including a couple of bad defeats in slam finals. Why the different outcomes? Well, I think one reason is that Wilander, with his "softer" game, gave Mecir much more time and space to work his magic. But Lendl was more direct and powerful, and he often pushed Mecir around and simply took control. The bottom line is that a good performance by Med against De Minaur doesn't necessarily imply that he'll look great against Sinner as well.
