1. Players: Along with Harper being gone, the Nats also traded away Daniel Murphy (2nd base). To replace Harper and Murphy, the Nats brought up Victor Robles and brought in Brian Dozier and midyear, Asdrubal Cabrera. Dozier and Cabrera are a good replacement for Murphy who isn't the player that he was 2 or 3 years ago. Robles is not Harper . . . yet, although he is much better defensively.
1a. Other significant personnel changes: Patrick Corbin is a great lefty starter that could be a #1 on many staffs. Juan Soto is a year older and getting better. Stephen Strasburg was healthy all year long. Kendrick is healthy and having a great playoff run. All four of these are significant changes over the previous year.

2. Clubhouse changes: Without Harper, Anthony Rendon was able to bat 3rd and become the silent clubhouse leader: Something that would have never happened with Harper still in the clubhouse. Mid-season, the Nats brought in Gerardo Parra who became the clubhouse soul of the team. He is just good enough that people will listen to him, but his personality and vocal leadership and penchant for loosening up the clubhouse and team made a significant difference to how the team played.

Are we seeing the Patrick Ewing effect? Maybe. This is not the same team as last year's team, but I'm not convinced that it is a better roster of individual players. However, they are a team this year. They have not always played as a team since Jayson Werth retired so maybe a version of the Patrick Ewing effect is being manifest.