The Nationals would have one of the top 3 offenses in baseball, Lester has allowed only one run in three consecutive appearances, this team could have made some moves at the deadline and been competitive at the end for a division like the NL east this year.
I think the problem in July was that the Nats could trust only Max to start given that Strasburg was determined to need surgery, and that Patrick Corbin continued to fall apart every start; in addition, the hitting disappeared when Kyle Schwarber got hurt and Starlin Castro was dismissed for domestic violence, and the boy-wonder CF, Robles, crashed. Schwarber had been leading off every game with a home run in June, so losing him might have made the difference. Yes, Schwarber was on an unusual streak, but even a good Schwarber might have been enough for the team to avoid trading away everybody, and, instead, to add an experienced starting pitcher (or two).
Think about the Nats at the end of June, rather than at the trade deadline. By July 31, there was no hope of winning.
Lester was the worst pitcher I have seen since some of the hopeless Nats teams of 2006 - 2009, or the expansion teams, or some of the no-hopers that Calvin Griffith collected in the late 1950s.