Best Answer:
Start with understanding Russia's plan:
https://www.reddit.com/r/geopolitics/comments/5hlgck/the_foundations_of_geopolitics_the_geopolitical/
https://warontherocks.com/2016/11/trolling-for-trump-how-russia-is-trying-to-destroy-our-democracy/
Among their goals is undermining democracy, journalism, promoting racism, sowing chaos/instability, separatism, and undermining general trust in public institutions. They've been doing this in many nations lately; notably Britain, leading to Brexit.
Also understand that Putin hates Hillary Clinton, particularly since she called out Russia's elections, embarrassing Putin and leading to widespread protests:
https://www.washingtonpost.com/world/national-security/us-intercepts-capture-senior-russian-officials-celebrating-trump-win/2017/01/05/d7099406-d355-11e6-9cb0-54ab630851e8_story.html
They also have the ability to control or strongly influence Trump. He has many ties to Russian organized crime:
Trump's mafia, criminal ties & activity
https://www.washingtonpost.com/investigations/trump-swam-in-mob-infested-waters-in-early-years-as-an-nyc-developer/2015/10/16/3c75b918-60a3-11e5-b38e-06883aacba64_story.html
https://www.theguardian.com/us-news/2017/nov/17/trump-ocean-club-panama-money-laundering-reports
https://www.thedailybeast.com/report-trump-panama-tower-riddled-with-drug-mob-money
* The reports detailed how the future president gave the project to his daughter Ivanka as a "baby" effort to gain real estate experience, and said it ended up drawing a cast of characters accused of fraud, corruption and kidnapping.
https://www.politico.com/magazine/story/2016/05/donald-trump-2016-mob-organized-crime-213910
http://www.newsweek.com/trumps-alleged-mafia-connections-sydney-casino-651352
http://time.com/4433880/donald-trump-ties-to-russia/
Source(s):
Dirty money: FT probe finds evidence a Trump venture has links to alleged laundering network
https://www.ft.com/content/33285dfa-9231-11e6-8df8-d3778b55a923
Ivanka was working with Russian mafia, journalist who helped uncover it (among other things) was assassinated
https://www.reuters.com/investigates/special-report/usa-trump-panama/
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