Trump was the most formally investigated president of all time; at least 4 formal investigations into corruption inside and outside the box. Even with partisan politics and constant trial by leaking to the media, the Democrats could not find any serious offense worthy of impeachment. If they had found anything real the Democrats would have used it.
Trump is not a man who is as pure as the wind driven snow. He has baggage. However, once he took office he has been under the radar, since day one, making it very hard to do anything illegal or unethical, since his critics are watching and ready to pounce. There are many Obama and Clinton holdovers, everywhere, sabotaging and leaking information. Trump has had to be very careful and by the book, making it hard to be corrupt, even if he wanted to.
Obama had the opposite situation. He was coddled by the media with constant sunshine up his skirt. If anyone spoke out, even with facts and truth, they would be labeled a racist to shut them up. The result was Obama had much more freedom to make many bad judgments calls, that were defended, but which would have been impeachable, if they could have been attached to Trump.
If Trump has sold uranium to Putin and Russia and then Russian gave the Trump family foundation a $100M donation, Trump would be impeached for that. If Trump had used the IRS to limit tax exemption status for left wing political groups, he would be impeached on that. If Trump had illegally sold guns to the Mexican cartels, so they could misuse the gun and thereby create an excuse to restrict the 2nd Amendment; Fast and Furious, he would be impeached for that. If Trump was been caught spying on journalist and then on an opposition candidate; FISA warrant, this would be grounds for impeachment. This is why much of the false accusations against Trump; Russia, were projected by the Democrats, based their own crimes. Ukraine is really about Biden and Obama and not so much Trump; Democrat projection for self defense.
Currently the Democrats have nothing as tangible as the impeachable crimes of Obama, to make the impeachment of Trump a consensus. The dual standard of the left, confuses the issue. If we assume one standard, Obama was far more corrupt or corruptible by the swamp than was Trump. The irony is the Democrats, by being such effective spies, gossips, foot draggers and busy bodies, have cut Trump's rope so short, he is unable to hang himself, even if he wanted to.
The Democrats have out smarted themselves and is it funny to watch. They should have cut Trump more slack so he had more rope, so maybe they would have caught him with too much rope, like Obama. Maybe in the Trump's second term they will learn and be more cooperative; longer rope.