It’s easy to look back now and ask why, but it was still unfolding. He did ask the Republican Congressional leadership about it and THEY said keep it quiet. And if he had said something, you know that Trump and all his supporters (and Fox News) would have accused him of campaigning for Hillary or being a fearmonger. I’m waiting to see what he’ll say in his upcoming book, though I do believe he should have told the R’s to shove it. He did it a couple of times. Why not now?
Why does the OP and other Trump supporters think that telling the campaigns would have made some sort of difference. And can you imagine telling Trump and asking him to keep it quiet so the investigation could continue. Uncle Blabby would be out singing immediately.
It’s a special skill to ask the same question over and over and be obtusely, intentionally deaf to the actual answer. The tactic depends on willful ignorance of both the utterer and the audience.
That’s why it works so well with Trump supporters.
Pretty sure Obama started a counterintelligence investigation headed by Jim Comey, and then Trump fired Comey because he thought it would stop the investigation.
Obama approached Mitch McConnel and said they should make a bipartisan statement so that it would not look political. He wanted to share with teh country what they knew - but at the time, they didn’t know exactly who - only that the hacks were russian in origin. They didn’t have enough information to indict anyone. But even if they did, without a bipartisan recognition of the facts, t would be perceived as obama using the power of the government to influence the election.