Looking at both pictures the chains seem very dirty, do you clean and lube regularly ?
erm it was 3 dry dusty rides old (152km in total)
definitely lubed before at least one of those 3
dirt has nothing to do with it
oh and it was a brand new chain, brand new cassette, and brand new chainrings on mine, before anyone asks.
edit: and it snapped my multitool chain breaker (which had already been weakened fixing someone else’s chain). I now carry a proper chain tool.
fortunately my emergency spares kit contains a €2 coin for the tram, and the app for the local transport co. which navigates you to the nearest tram stop (and lets you buy e-tickets too)