Viruses sometimes disguise themselves with the name "wuauclt.exe" or intentionally break the update service to prevent security patches from being installed.
Overly aggressive third-party antivirus programs can block the update client's network requests, causing it to hang or crash. "Best Work" (Solutions & Best Practices) why does wuaucltexe crash best work
There is no single reason. Instead, the crashes stem from a handful of common failure points: Viruses sometimes disguise themselves with the name "wuauclt