It's very clear.  Trump has been trying for years to get in with Russian oligarchs to do real estate deals.  Up to now he has been unsuccessful to get into the Russian market, although he has been successful to get the Russians to invest in his property outside of Russia.  As Donald Trump, Jr., said about their business:  “Russians make up a pretty disproportionate cross-section of a lot of our assets -- we see a lot of money pouring in from Russia.”

The reasons for Trump currying favor with Putin (and the oligarchy) is clear.  He thinks it is his way into their market and to get them to invest more into his company.

I find it amusing to see Trump supporters get all bothered because Hillary Clinton derived a mere 8% of her speaking fees from financial institutions, yet Trump is deep with the Russians financially.

https://www.washingtonpost.com/politics/heres-what-we-know-about-donald-trump-and-his-ties-to-russia/2016/07/29/1268b5ec-54e7-11e6-88eb-7dda4e2f2aec_story.html