First of all, you say that 80% are "affected," and that $216K is their median income. You don't say what you mean by "affected." Evidently you mean their taxes are affected in one way or. another -- up or down. (You must mean by that because you say that 30% would have an increase in taxes.) If that's what you mean, then the 80% figure is meaningless. Even if the 80% figure means more than that, it has no significance. 216K is, I take it, a median, although you don't specify. That means that 50% are above $216K. That 50% includes people making a heck of a lot more than $216K, e.g, a million. By definition, a deduction helps those with the most to deduct. The people with the most to deduct in state and local taxes are, naturally the richest. Having an unlimited SALT deduction helps the rich the most.
https://itep.org/not-worth-its-salt...whelmingly-benefits-wealthy-white-households/
Edit: keep in mind that limiting the SALT deduction was part of a package that cut tax rates for everyone. If limiting the SALT deduction raised taxes for 30% of New Jerseyans, then it must have help reduce taxes for the other 70% -- who were not as rich as the 30% who saw their taxes increase.