When the season started out as bad as it did, there were some people, including on this forum, that said this was what the team was, and our division wins in previous seasons were only because of how weak the rest of the NL East was. Now that the Braves, Mets and Phillies were contending teams again, so it was said, it was shown that the Nats were the emperor who had no clothes.
This season certainly demonstrated that there was greater parity in the NL, especially in the non-Marlins East, and thus a tougher row to hoe. Even the Pirates, who ended up with the 2nd worst record, were one game below .500 at the All-Star Break. And the Padres were at .500 at the All-Star Break. And how many NL teams were still in the Wild Card hunt in September, when the AL was practically wrapped up? So, as others have said, perhaps one of the biggest differences this year was that the Nats had to work for it that much harder, with no rest in September.
That makes me wonder about these 100+ win teams. There is no doubt the Astros, Dodgers and Yankees were objectively good teams, with strong line-ups and good pitching (more starting for the Astros and Dodgers and relief for the Yankees). And the Twins for that matter. But were they objectively that much better than the 93-win Nats, or did they benefit also from their schedules? In other words, the Astros and Nats were a lot closer matched than 107 wins vs. 93 wins would seem to indicate.
Of course, playoff baseball being what it is, the Brewers were only one bad inning from beating the Nats and advancing, and the Braves were one disastrous inning from possibly beating the Cardinals, making for a completely different postseason.
This is why I like baseball. Getting to where the Nats are was the outcome of a season where dozens of teams playing hundreds of games, batters stepping into the box thousands of times and pitchers throwing tens of thousands of pitches. Over the course of the season there are so many numbers to crunch and you can pick out so many moments to say "what if" (what if Grisham handles the ball and it's at best a tie on Soto's hit?), but in the end, there can be only one. And it is some other team's fans spending the off-season doing their version of "what if Drew Storen did this" or "what if Dusty Baker did that" or "what if the umpires made the right call on that", etc. And we get to go watch a parade.