Huh??? Just huh??? This was a private business deal that Trump began working on before he ran for office. There is nothing illegal about a candidate engaging in legal business with a foreign nation.
And, by the way, Trump has been far tougher on Russian than Obama was. Trump has sold Georgia and Ukraine weapons, while Obama refused to do so. Trump has slapped tariffs on Russian steel, which Obama would not do. Trump has pulled out of the Iran nuke deal, a deal that Russia supported. Trump has expelled dozens of Russian diplomats and shut down one of their consulates, something that Obama never did.