Because weak clown Robin, who wasn't able to do a shit to Diamante could threw Yonko. I'm absolute positive in SH becaming stronger, but not like that. She didn't surpass her limits, she was never strugling, she is weaker than King and Queen, Queen who was neg diffed by BM without haki. This is riddicules dog shit. This is worst way how you could crush readers ecpectations. Absolute trash.