The shiny ends of the top ring tell me they were either ground on for getting the end clearances proper or they butted and that led to much tension leading to that one breaking on the other side of the gap or something I haven't seen like that yet
It doesn't look like the two broken half's touch each other while it ran also
That small black dot on the top edge of broken ring may have caused it to fail while being installed or shortly there after
Did you check all the rings for proper back clearances in the piston ring grooves by pushing them in far enough to clear the pistons sides? If they are too thick and won't slide back into the grooves all the way that can cause them to break also