Here is one bit, there is more analytical political science at the link:
5. Trump’s foreign policy advisor on Russia and Europe is Carter Page, a man whose entire professional career has revolved around investments in Russia and who has deep and continuing financial and employment ties to Gazprom. If you’re not familiar with Gazprom, imagine if most or all of the US energy industry were rolled up into a single company and it were personally controlled by the President who used it as a source of revenue and patronage. That is Gazprom’s role in the Russia political and economic system. It is no exaggeration to say that you cannot be involved with Gazprom at the very high level which Page has been without being wholly in alignment with Putin’s policies. Those ties also allow Putin to put Page out of business at any time.
Recommended reading for your final exams in public choice. Do read it all.