It makes sense that he'd understand how America's enemies think, because he thinks like our enemies. Many of his suggested policies most resemble those of authoritarian regimes America has battled militarily and with sanctions.
When he claimed that he'd encourage China to invade North Korea in the first presidential debate, it was deemed reckless by military leaders and other professions which require a basic grasp of the English language. But who else would you trust to understand North Korean leader Kim Jung-un, a sociopathic narcissist known for his weird hair and aggressive stance toward his neighbor to the south? Who better to relate to North Korea's Dear Leader than someone who also seems to believe his own propaganda, despite inheriting his privileged position from his father? Hell, it's often impossible to differentiate North Korea's propaganda from Trump's political messaging.
For instance, see if you can tell which of these quotes is from Donald Trump, which was said by Vladimir Putin, and which was said by Kim Jong-un:
America is "very weak and ineffective."
The American "military is a disaster."
America is a "third-world country."
Hard to tell right? Well, it was a trick question. They're all Trump. (Kim Jong-un usually speaks in Korean.)