It didn't have to have had a visible crack or anything, Metaphor. Just some undectectable, invisible weak spot was all it took. Glass is wacky that way.

Cutting glass, like for window panes, mirrors, table panels, or stained glass is essentially a matter of controlling the fracture process in a precise way by breaking (scoring) the surface tension evenly and then helping it break along that score line. Wish you lived near me. I'd cut you a new panel for that table out of some tempered glass that'd be a little more resilient.