The remarks in this video from Trump's press conference are very emblematic of the way he operates.
There are two aspects here that I'd like to dive into.
One is that Trump's understanding of national security comes down to his own well-being. His concerns in having someone testify who "knows some of [his[ thoughts" is that if Bolton says something negative, it will make it harder for Trump to manage diplomacy... his style of diplomacy consisting largely of trading compliments and threats one on one with other foreign leaders.
It's not that Bolton might let slip something classified, or reveal something about our strategic goals or defensive capabilities. It's that he might repeat something Trump said about another head of state, undermining his ability to craft his own narratives by saying different things to different audiences and hoping they never find out what he told the other.
In this respect, Donald has indeed tried to run the government the way he runs his business, where he might tell a licensing board one story and regulators another and investors yet another story entirely in order to get each group to give him what he wants so he can get a building with his name on it and a pile of money to fritter away on his "billionaire" lifestyle while the actual business venture slowly rots from the inside out.
If Bolton were to go around telling the world what Trump says about his marks in front of US officials, it will make it harder (not impossible, just harder) for him to snow them.
That, to him, is a national security issue. It doesn't actually endanger us as a nation. It doesn't weaken us, unless you think his ability to rack up paper "wins" and brag about them somehow diminishes us. But it makes things work for him, and to Donald Trump, he is the United States and the United States is him: l'état, c'est moi. The state, it is me.
The second aspect is yet another case of Saying The Quiet Part Loud.
When he talks about not wanting Bolton to testify because he left on bad terms, he's admitting that his whole calculation here is, "Is this good for me?" He sees the world as people who are reliably useful and... well, enemies. It's no exaggeration to say he wouldn't be in office now if not for Jim Comey's actions in October of 2016. Analysis from both campaigns bears this out. The FBI under Comey publicized the trumped-up email laptop investigation into Hillary Clinton and quietly kept a lid on the investigations into Trump's campaign and foreign influence.
They weren't uniformly in the bag for Trump, but there's no rational analysis that says they were against him.
Again, he wouldn't have won without them.
So why did he go after Comey with such a vengeance?
Because knowing he owed his throne to Comey's intervention, it became imperative that Donald owned Comey. If Comey were a free agent, acting on his own agenda or even merely doing whatever he thought right, then the power that elevated Trump to the highest office in the land could be turned against him. He had to be sure of Comey's loyalty, or destroy him.
Comey made it clear he wasn't going to be Donald's creature, and so Donald sought to destroy him.
So here we have John Bolton, whose testimony could exonerate Trump or damn him. He left on bad terms — and we should note that when Trump says that was his fault, he's not taking blame for the rift but credit for having fired him, a backwards-facing dig at the dispute in the order of events — and that alone is reason enough for Hair Furor to fear letting him testify. He isn't a reliable tool and this makes him a threat.
None of this is new insight. It's just more being added to the preponderance of evidence that Trump is a dictator in the making. The sad thing is that even when he says on TV for the whole world to hear that he's making his decisions purely on the basis of what's good for him as an individual, the specter of executive privilege may be enough to forestall crucial witness testimony in the trial as it did during the hearing.
Thank you for reading!