As
@tsubaki rightly mentioned, the person or people who committed to crime are ultimately the blame for another tragic death and no one is saying otherwise.
Yet, let's not be ignorant of the elephant in the room. I'll give you a layman's example of how numbers of boots on the ground has changed over time.
Let's say in the 80s or early 90s, on nights from a nick in Liverpool there was at least sixteen on parade: ten on the beat and least three cars double manned.
There was six stations in South Liverpool, with similar ratios based on their patrol area, so on nights you can work out how many cops were on patrol at night.
Now? There are two nicks covering the same total area and you'll be very lucky to get ten on a shift from each station with huge areas to be covered on patrol.
No one patrols the beat and they are simply on response, which removes very little flexibility for pro-active patrols. This is with a growing population as well...