Trump never hid the fact that he wanted to be Putin's *****. All during the campaign, and years before his candidacy, Trump trumpeted his infatuation with the murdering dictator.
So collusion or no collusion, Trump was always going to ease up sanctions on Putin. Putin didn't even have to ask.
Putin knew this, and that is probably why he decided to help Trump get elected. There really was no need for them to collude.
Nevertheless, there are indications of collusion between members of the campaign and some of Putin's cutouts.
Trump easing up on sanctions against Russia is wrong. You can call it wrong all the live long day, but it would not be illegal for Trump to do so.
You might not like it, I sure wouldn't, but there is nothing illegal about it.
Just like there was nothing illegal about Obama announcing way ahead of time he was going to cut and run from Iraq, and then following through on that promise.