All politicians have "something to hide". One of the reasons I have been hesitant to run for office locally is concern for dirt that might be dredged up or made up. Not that I have tons of skeletons in my closet, but the intrusion into people's private lives is horrible.
Trump likes to think that he is unique, as in special and gifted. He isn't. The only thing that sets him apart in any positive way in his life, was that he was born to wealth. He is unique however, in that he is SO DAMAGED and SO NEEDY that he us uniquely susceptible to being compromised. It doesn't even really stem from all the horrible shit that he has done either. Most people know he is a scumbag and has likely done worse that what is being exposed. The problem is that to Trump, his IMAGE is his only concern. Trump doesn't require blackmail to give up state secrets, the only thing he would really need would be for something to benefit him in some big way. Putin was able to play him easily and the Chinese had him begging and trying to exhort the Congress to take one of the tech companies off the bad list because they (the Chinese) buttered him up and probably offered to spend bunches of money at Trump properties.
Like I said, people have secrets. What Trump lacks is what makes him unique. He lacks any integrity or ethics.