Have I been in a life-long bubble such that the ordinary explanation of "bus factor" seems so mild that until reading exchanges like this a couple times it never occurred to me it might be morbid enough to bother someone? Or is this one of those things where people are looking for something to worry about but it's actually entirely fine? Like, I've seen children's cartoons with jokes that were more morbid than that.

(I do also like the lottery version and use them basically interchangeably, though the shorthand is always "bus factor" for me)

Phrasing "getting run over by the lottery" sounds like a good humorous, compromise. But "winning a bus" sounds like you're actively rooting for the person to be hit. I'd stick with the former. ))