Excel would use 100% CPU if you left a cell selected and your screen saver turned on because you were idle.

That bug caused untold grief for multi-user session hosts / terminal servers / Citrix XenApp for a better part of a decade. Way before slopware!

People forget that software written by people is… even worse.

It’s like the self driving car debate: sure, the robot taxis will kill people on occasion, but people kill people reguarly.