Not necessarily your fault, that seems to be a common failure on 7020/8020 levers. There's a grub screw in the side which acts as a weak point/stress riser/crack initiator
Yeah, the interwebs seem to indicate it's a poor design. But one that seems to also afflict GRX as well. So it feels like playing lottery with whatever option I can stomach to overspend on
So put too much torque down? I used a light touch to cinch it down, just i had done with the left. Guess I'm gonna need to get a replacement. Bugger