I don't see it. Crime is up on the subway, so you think this is part of a politically motivated strategy to "[hold] back the police force from doing their jobs"? The article says they have a lot of vacancies. Maybe they can't find people who want the job? Maybe their budget for policeman salaries doesn't fare well compared to the area housing prices? I could think of quite a few possible reasons for a rise in crime before getting to the idea that this must be some leftist plot to help the criminals.

A track record of holding police back from political protests isn't relevant. There's no political group supporting these robbers.