Doing some research into how glass can break, and stumbled across inclusion breaking. What this means is that the microscopic shavings of metal from the glass-making process can contaminate the glass during the forming process, creating hidden internal stress. The metal shavings change structure over time, eventually exceeding the strength of the glass. To quote Wikipedia:
This type of breakage is almost always found in tempered glass and is indicated by a distinctive “figure eight” pattern, with each “loop” of the figure eight approximately 30 mm in diameter.
I find this absolutely fascinating that glass can break in a very specific way depending on how it’s made. Makes me want to revisit the Corning Museum of Glass in New York again as soon things return to normal.