I think this kind of brings up an interesting point about the Trump Presidency. In a normal world, a President would have to put some kind of "signature" on the bill. They would have something they ran on in it so they could rest on it. Trump doesn't have that, he never has given specific plans or ideologies. So, like many have said, this has no direction. Trump is okay with whatever, as long as it's Republican. The problem is that not all Republicans will agree (see Rubio tweet). This, along with Trump, should be a disaster moving forward. I'm just hoping there is someone in the RNC that can slow this disaster down a little.
I personally think he just doesn't want to upset the apple cart.
I think somewhere along the line, someone planted the seed "20% corporate tax rate" was the most important goal in his head. He decided it was a tremendous idea & 20% was a nice, round number that was easy to grasp and hock to people, and here we are.
There's also the fact that Trump doesn't really give a crap about the middle class or certainly the lower class. It's prudent to remember he's never really interacted with any of them outside of rallies or hocking his own crappy products & actually made a living stiffing them in the form of contractors and others with whom he did business. Given he never really had to interact with them & probably doesn't have any real friends in the middle/lower classes, why would he care what the tax bill does to them? Of course, a rational president would want to pass a tax bill that was, you know, popular... but Trump ain't that. He has a very strong penchant for just doing whatever he wants, consequences be damned.
It's fairly evident that for all their rhetoric, the GOP who actually structured this bill doesn't appear to care about the middle or lower classes all that much, either. But if they did, they wouldn't have tilted so egregiously towards the upper class and ultra-wealthy. They also wouldn't have tried to shred healthcare for the lower and middle classes. Sure, they doubled the standard deduction. But they seem to be existing in a universe where they've imbibed their own rhetoric too heavily and have begun to believe it lock, stock & barrel. They reject the analyses that predict this bill isn't structured well enough to not underwhelm & tack trillions onto the debt because, well... liberals obviously have the facts wrong and they don't like those mathy types.
Trump doesn't dare inject reservations into the debate. He knows he can just blather lie after lie about what the bill will do instead and a certain portion of the population will lap it up. Besides, if they had to restructure it, it might cost him personally something like the repeal of the estate tax or alternative minimum tax, which both benefit him tremendously. I'm operating under the cynical assumption he merely wants a bill to pass & to personally benefit financially as much as possible, while the rest of the details are frivolous and ancillary.
The most disappointing thing is the utter lack of anyone in the GOP standing up to Trump. Several people have the power to bring this damn thing to a screeching halt and get whatever recessions they want. But they fear his tweeting fingers and meekly watch something they don't really like chug along. Nobody will stand up to this guy. The closest we've got are a couple of soon to be retirees, a woman operating on a good-faith handshake deal with a couple proven liars & a war hero likely to soon shuffle off this mortal coil with most likely terminal brain cancer.