Google makes a lot of money from app developers. Perhaps they decided that the cost to them of angering app users by deleting negative reviews is less bad than

Google makes a lot of money from app developers. Perhaps they decided that the cost to them of angering app users by deleting negative reviews is less bad than the cost of app developers leaving their platform because Google won't protect their reputation (whether the negative ratings were deserved or not). App developers can watch this and rest easy that Google has their back in this (even if they don't on other things).