The goal is to neutralize them by diminishing their enthusiasm.
Many people liked Trump because he was (1) wealthy (2) a success at business and therefore (3) beyond corruption because of his wealth and thus (4) free to speak the truth as he saw it.
But none of those are actually true:
He is not as wealthy as he claimed, but deep in debt, much of it to foreign banks and shadowy Russian businesses.
His reputation as business leader depends on overspending on his projects and then going into bankruptcy. Businesses can advantageously go bankrupt. The US government cannot. His particular business skills are irrelevant to the job of being President.
His debt and obvious cash flow problems are forcing him into corruption. He is selling the Presidency for quick profits. A truly wealthy person would divest and liquidate his holdings, content to live the rest of their life on the profits accumulated over the years. But Trump's refusal to divest means that he needs to continue to make money through his businesses. He is probably too indebted to liquidate. If he sold everything, he wouldn't make enough money to pay his debts.
And yes, he speaks whatever is on his mind. Unfortunately, it is the incoherent bluster of a profoundly uninformed person.
There was a certain logic for voting for Trump. But you have to see that the logic for Trump has turned out to not make sense.