Ordinary people who identify themselves as Democrats have a variety of mostly noble intentions and desires. Elected Democrats in Washington, D.C., are another matter entirely. When voters gave them majorities in Congress in 2006, telling exit pollsters that the top reason was to end the war on Iraq, Rahm Emanuel openly told the Washington Post they planned to keep the war going in order to run "against it" again in 2008. And they did. And it worked. And it was all open and transparent, but nobody really cared. Refusing to end the war or impeach Bush was ranked as "less evil" than being Bush.
If Democratic politicians had some desire to accomplish something (ending wars, saving the earth's climate, closing prisons, whatever) they would work to create a culture in Washington in which those who abuse power are held accountable, subpoenaed, held in contempt, impeached, removed, unelected. Because their only goals seem to be staying in office, pleasing funders, getting on TV, etc., they are the top supporters of keeping Donald Trump in office through 2018, after which they will tell us that it would really be best to keep him around and run "against" him again in 2020. Republicans, in contrast, are generally turned off by such prospects.
The Democrats' cynical calculation is the source of a great deal of the "Pence would be worse" malarkey we hear. In reality it doesn't matter who comes next in comparison to whether who comes next can be held to the rule of law. But you won't convince an elected Democrat of that. Instead you have to convince them that we will make their lives a living hell unless they impeach Trump, and that impeaching Trump will win them support.
If Democrats cared about either doing their job or removing Trump from office, they would be going after Trump right now for illegally shooting down a Syrian plane, illegally drone bombing numerous nations, conducting numerous illegal wars, illegal prejudicial bans on immigrants, illegal willful destruction of the earth's climate, unconstitutional domestic and foreign profiteering from his public office, and a whole laundry list of crimes from sexual assault to voter intimidation.
The Russia obsession has, I think, three clear motivations:
1) It shifts blame from a broken U.S. election system, a lousy
Democratic candidate, and the DNC's rigging of its own primary to a
2) It sells a lot of weapons.
3) It keeps Trump in office.
Is that third one the hardest to understand? Think about it this way: If you wanted to "investigate" one of the other charges I list above, the investigation would be instantly over. The evidence is public and beyond dispute. But if you hold "investigations" of vague Russian something-or-other, you can go for months or years with the top news story being whose lawyer hired their own lawyer and other tangential cow pies, keeping "Trump did some evil treasonous thing" in the news for every crazed gun-owner and potential voter to hear over and over again, without actually removing Trump from office.
Of course, I'd love to be proved wrong. That would require action by members of Congress.