NJ essentially aims to be the suburb of NYC and Philadelphia.
This is exactly correct. Its politics are dominated by the philosophies of Philadelphia and New York City.
As New York City and to some extent Philadelphia went through gentrification, becoming too expensive for much of the social classes it was once known for, they primarily moved to New Jersey.
Where there was a lot of industrial work.
Many of the middle and upper class residents from the cities also choose to get a home in a suburb of Jersey.
I would say half the people in New York City who decide they want to get a nice normal house and raise a family rather than live in a NYC apartment head to Jersey to accomplish that. (As the houses in NYC are limited and very expensive.)
New Jersey is more closely culturally associated with New York City and Philadelphia than most of New York state or Pennsylvania is associated with either city.
No big expensive city can live in a vacuum without industry and labor forces. Yet through gentrification the cities became too expensive for most of the labor they need to run. With a desire to be "cleaned up" they killed off most of their industry.
Most of this industry relocated to Jersey, and as a result much of the crime did as well.
The home for everything the cities don't want? Jersey. Whenever you hear a Phily or NYC mayor say they cleaned up crime or something else in the city? It just was pushed into Jersey.
Since much of the population of Jersey is connected to one of the two cities, the philosophical and political veiws of those cities dominate.
With nearly 20% foreign born immigrants, and lot of industrial work, and a street culture like New York City from decades ago, Jersey is what NYC was known as last century. Where New York City and Philadelphia have become too expensive for most of the labor forces that once made up its diversity Jersey has swelled with their ranks.
So Jersey swelled with the ranks of most of the portions of City society responsible for crime when those lower income individuals were forced to move from gentrification.
It also has tremendous population density.
For containing most of the labor forces of the big cities it also has a very high median income and a lot of middle class and upper middle class commuters.
Which tells you there is some very clear class differences living in close proximity.
My experience is when you put a lot of relatively wealthy people next to poor people, and throw in some cultural diversity, you end up with gun control laws and a permit system which favor arming and protecting the former over the latter, or at least hiring more LEO and security for the former, and disarming the later.
Money is after all what drives political power. So those with the money make the system favor them.
So you have a number of related influences that are going to greatly contribute to an anti-gun mentality in Jersey.