The national GOP simply used this as an opportunity to screw a bunch of deep "blue" states. As one astute observer pointed out, there are six states that are screwed particular badly by this tax law -- California, New York, New Jersey, Massachusetts, Connecticut and Illinois. These are the states affected most by the combination of two factors in our tax code that screw middle-class people: (1) the high cost of living pushes middle-class people into upper-income tax brackets, and (2) they have ridiculously high state and local taxes that now have deduction caps.
In a Senate where the Republicans only held a 51-49 majority, this tax bill wasn't killed on the spot because there wasn't a single Republican U.S. Senator among the twelve representing these six states.
There is a decent argument against that particular break, and if they had only phased it in over time it would have been okay — especially if they had dropped the material rates in offset.
But what did they put in there? A huge tax break, for example, for the class of Javanka’s pals in Manhattan who hire expensive nannies and send their kids to expensive private schools.
Likewise, they supposedly were helping inner-city blacks with ‘enterprise zone’ legislation. But what they really did was provide big tax breaks for big slumlords—like the Kushners.
Trump also campaigned on totally eliminating the estate tax, which would be a massive boon to families like his, though Congress only allowed a doubling of the exemption to $11M to get through.
The problem is that the scenario I laid out will play our across all fifty states; while more people may be hurt by the SALT limitation in the six states you describe, people in all 50 states have lost their exemptions - therefore more of their income is taxable, and it is a question as to whether or not the increased standard deduction and/or child tax credit offsets the loss of those exemptions.
Again, I wasn’t hurt by the SALT cap, but by the loss of exemptions - and I suspect many more people are going to be furious when they realize the “raise” they received last February was a hoax - they’ll pay that back and more.