No Logic does not so dictate. For one None of them were Billionaires who had their position already earned before they negotiated with the donors. So Money and Power were not what was the asset they could use to gain control.
As far as the others yes, They are Nothing without their donors, No political life, no office etc. Trump showed he could do it without their help. He does not need them but all the normal politicians do which is why the Donor class normally is the ones in power with the elected ones merely a figurehead who does what they are told. Its about who controls whom. Trump has the power position not the beggar position like the others.
Still can't let go of "They are all crooked except Trump", can you?
Let's try it this way.
Let's make the assumption you are 100% correct.
I am a big donor who has donated to Cruz/Rubio/Kasich/Carson/Christie/Bush, etc,etc,etc, because I expect to buy influence.
Now that all of them are out of the race, I will donate to Trump because I expect to buy.... oh wait, he can't be bought, now what?
I will now donate to Clinton because I expect to buy influence. We know Hillary is for sale, right?
In you world, I cannot now donate to Trump because I have lost the ability to buy influence, so why bother.
BTW, none of them are "billionaires" except Trump, but it is not like any of them are going into the poorhouse anytime soon.
Either these donors, who supported others, now courting Trump, are expecting to have influence or they are not.
It doesn't change simply because the nominee changes.
My logic still stands.