It's odd, but I've seen it happen before. Going down the road our rigs experience a 3-5 Richter scale earthquake, the sidewalls are flexing, thus the window frames are flexing. One thing causes a bit too much concentrated pressure and the tempered glass shatters. Or it could have been a rock from another car, glancing it just right. Whomever fixes it will hopefully inspect the channel for anything like a screw that's too long or something else in the area.
If your ears weren't popping, the pressure should have been fine. It takes a lot to push a properly installed window out, you'd have known it had that been the case.
Now-2014 Sierra 346RETS 5er BUB
Then-2002 Keystone Springdale 286RLDS TT
Nights camped in 2014-28, 2015-127, 2016-10