Why does Trump avoid discussing his communications with Vladimir Putin while openly bragging about calls with other world leaders?

In the clip, Rachel Maddow highlights a striking contrast in Trump's communication style regarding foreign leaders. Trump readily brags about and publicizes his conversations with numerous world leaders, including controversial figures like the president of Communist China, openly sharing details of these interactions. However, when specifically asked about his communications with Vladimir Putin, Trump's demeanor changes completely. Instead of the same openness, he dismisses such questions as 'inappropriate' and refuses to discuss these particular conversations. This selective transparency raises questions about the nature of Trump's relationship with Russia and what might be contained in those undisclosed communications.