There's no reason to keep her around either. Every time there's a new protest, the first demands are: 1. Full withdrawal of the extradition bill, 2. Carrie Lam resigns. The bill is politically unviable for the foreseeable future, and Lam is its figurehead. If they want to take steam out of the protests, they need to address these sticking points.

If they have a new CE come in, fully drop the bill, and actually set up an independent investigation into police brutality, it would take a lot of wind out of the sails of these protests before people dig their heels in on other issues (abolish the functional constituencies, establish universal suffrage, etc.)