Big, Democrat-run cities like Philadelphia bring this activity on themselves with their decriminalization policies that have empowered people to commit crimes without fear of punishment. Types of activity like coordinated "flash mob" robberies are a feature, not a bug, for Democrats who think that their reckless policies will help them at the polls.
Republicans should stop politicizing crime, which is up across the nation. It just so happens that Democrats are in charge in most cities — where crime is naturally higher because of density and other factors. But there are plenty of Republican-led cities dealing with a crime surge. The economy, social services, and other aspects of society affect crime rates more than the political party in power.