Because they are flown really, really often.
Their mission per crash rates are actually quite equal to F22 and F18.
Also every time they crash it's reported.
Countries that operate F35s tend to train with them a lot, and the singular airframes are kept in the air for longer periods of time.
You also gotta remember that some +700 of them have already been made. So of course some Meme machine from China/Russia etc that has 10 prototypes and 5 production models ready won't crash at the same rate.
Another thing is also that USA is quite open about reporting the issues. Even countries like France, UK, Germany tend to hide all the failures. Those planes do have issues, but they less often are discussed about.
That being said, i am very biased, as my motherland just bought F35s.


