Serious Question - Re: Tax Reform

These wealthy GOP supporters who are demanding tax reform...

I assume they are basically intelligent people.
I assume they know something about economics.
I assume they know something about the Kansas experiment.
I assume they really don't want to destroy our economy.
I assume they are not monsters who are net seeking infinite wealth.
I assume they are aware of the questionable success of "Trickle Down".
I assume if they are engaged in business they want a middle class who are active consumers.

So, if I assume they think this Tax Reform bill is good, on what theory do they base their opinion? Is there one out there?

I really would like to know about the other side of this argument. And I do not feel I can trust anything GOP congressmen say since I believe there motivation is to appease the donors.