“since Trump could not accomplish the prosecutions and convictions of Holder and others who deserved such”
I think it’s more like, “Trump WOULD not”. Maybe he did, but I don’t recall him bothering. It’s like he believed — and he did believe — that once he was president all of the past would be over and done with. With RATs, it’s never over and done with; they just regroup and find more energy.
Your assessment of Trump’s personality may be correct. He does not seem the vindictive type, to me.
He has paid the price for this, though I would not be surprised to see no change in his behavior, should he enter the White House, again.
I, personally, do not feel that he was, in any way, a free actor in his first term.