Maybe he is just running out of gas.., I mean to be at that level in the last 3 events surely takes a toll mentally and physically.
There is definitely something to be said about that. We have seen it happen with some of the greatest players in tennis history. After McEnroe beat him in the finals of the US Open in 1981 in 4 sets (which came on the heels of a 4 set loss to McEnroe in the 1981 Wimbledon finals), Bjorn Borg left the court before any press conferences and went straight to the airport, and never played another match on the regular tour again (he later apologized to McEnroe, who became a great friend of Borg in later years). This was sad, because although McEnroe beat him in 2 major finals in 1981, Borg won the French Open that year, and he had actually won 3 majors in the prior 3 years without dropping a set! I am old enough to remember those matches, also including the legendary 1980 Wimbledon final in which Borg beat McEnroe in 5 sets (later turned into the Borg v. McEnroe movie that came out a few years ago), and it was the greatest tennis I ever saw. There was a great contrast between the 2 players because McEnroe was very likely the most talented serve and volley player in tennis history and had an unmatched assortment of creative volleys and serves (very high ball toss that confused opponents and was able to place the serve whereever he wanted). Borg, on the other hand, was the master of baseline groundstrokes with massive topsin, but he could also serve and volley when he needed to, and he was incredibly fit and had great stamina. Both players respected each other and brought out the best in each other.
Just a few years later, almost the same thing happened with McEnroe. In 1984, McEnroe won 13 ATP tournaments and compiled an 82-3 match record, the best single season in the history of Open Era tennis by any male tennis player. One of those 3 losses came at the French Open finals, when he blew a commanding 2 set lead and lost in 5 sets to Ivan Lendl, who had nowhere near the talent of McEnroe but was bigger, stronger and fitter, and wore McEnroe down in that match. McEnroe bounced back to win Wimbledon and the US Open, but his 1984 US Open title was his last major. He made one final in 1985 (losing to Lendl at the US Open), was clearly burned out and then took a long sabbatical in 1986, after which he came back and was never remotely close to being the same player again.
I view Borg and McEnroe as 2 of the most talented players I have ever seen and both had their career at the top come crashing down fairly quickly. Felix is only 22, and he is still on an upward trajectory, but he will need to be careful about too much because I really think that playing in all those finals over short spans of time ruined Borg and then McEnroe. They each had several years of very dominant tennis and probably played too many matches and certainly too many intense matches, including against each other.