Actually the Democrats could have impeached Trump on other things because he was breaking the law and basically running a criminal enterprise out of White House from Day One. He was violating the Emoluments Clause of the Constitution from the day he stepped into his office.
That clause means the President absolutely cannot use his position to make money for himself in any way whatsoever. So if a President has a lot of stock in a company, he can’t do things to push the stock price up so he can get rich.
All Presidents in the past have always divested all of their money-making assets (note that this doesn’t include personal property like your home and car) or they put it all in a blind trust.
Divesting means if own a lot of stocks or other money making entities like businesses, resorts, hotels or other property you don’t live in, you have to sell all of that stuff or at least your share of it before you come into office.
So Trump have had to have sold all of his money making real estate or better yet, just resign his position in the company and sell his share of the it before he took office.
People might argue that it would be unfair to force Trump to sell of his money-making property, but if he sold it, he would end up with a huge pile of cash in his hand. On the other hand, the property keeps making money and the cash doesn’t unless you put it into CD’s or something like that.
With a blind trust, you can’t see what’s going on with your money, so there’s little motivation for corruption. Trump was doing favors for other countries in return for them letting him build casinos and resorts from the first month of the new government. The very crooked Ivanka was doing the same thing. She’s also loaded to the gills, by the way.