I said this before, but I'll say it again. When Trump hosted Russian diplomats/spies at the White House, when he confiscated his translators notes after a meeting with Putin, when he had another meeting with Putin with no US translators present, when he left the Kurds high and dry, the press would ask, "why would Trump do this?"
Every time Trump did something inexplicable, there were always a range of explanations. However, there was one that explained them all.
There is a trail of circumstantial evidence he has been a Russian asset since 1986 at least. I suggest you read American Kompromat by Craig Unger.
Just be careful because a lot of that info comes from a former KGB asset, so there's certainly an agenda there. That doesn't mean the info is wrong, just that there's likely more to the story that we don't have access to.
In the book, Unger cites ex-KGB officer Yuri Shvets in making the case that Trump's relationship with the Russian government started decades before he became president.
...
In a book review about "American Kompromat," John Sipher, a retired member of the CIA's clandestine services, concluded that the book doesn't necessarily reveal anything that was previously unknown about Trump, who has long been a public figure and whose activities have been widely covered for years. It "reminds us that there is still much left to learn," Sipher wrote.
So my take is either the information is correct, not dangerous, or the book isn't popular enough for the interested parties to take it seriously. I don't know why US intelligence operatives have been silent on the issue, that's why I hesitate to take the book at face value (maybe they see him as a victim, or perhaps they need a smoking gun).
That's the best I have. I would really like to hear what the Trump campaign has to say about it. They'll probably just deflect though.