He would have been wise to climb as high as he could, way above the usual coastal fog that is always there this time of the year.
Instead, he was down close, trying to fly under the fog, and ran out of space as the terrain came up.
Probably went to climb, and almost had it, doing it right, then took his eyes off the instruments, looking out the windshield, and used his middle ear to navigate rather than his eyes on the attitude indicator.
pilot error, 100%.
happens real fast, in real time, no do overs.
Plus the moron was doing 150knts or whatever.