nothing happened 'to' him. he took that fairly united party and told whole sections of it to piss off. banging the anti-immigrant drum won zero votes and alienated many. he was all blunders. centrist is a blunder
Seen from abroad it's hard to make sense of what happened to Starmer. Big majority, centrist, fairly united party, no obvious blunders -- and somehow it went off the rail in just a few years. Political scientists will have their work cut out on this one.
