If you think he didn't, what's the evidence?
I preface this by saying it's been a while since I kept up with Russia-gate and I've not explored Tulsi's purported bombshell too deeply, but with that disclaimer out of the way, based on what I actually
have read and heard, I think the most plausible scenario (in my mind, anyway) is that intel agents/analysts investigated the supposed Russian hack theory and concluded that the evidence wasn't there. That does not necessarily mean that Russia or some Russia-aligned agent
didn't hack the Clinton campaign's emails, but investigators just didn't have technical evidence to support it, which supports what the MAGA-verse has been arguing all along.
Unfortunately, it seems to me that what may have also happened is that senior folks in the IC (especially Clapper, Brennan, and probably some foreign policy/intel wonks in the Clinton campaign, possibly even Hillary herself) were so convinced that Russia had such a hard-on for Sec. Clinton and were therefore so adamant that Russia was behind the hack that they concluded that absence of evidence in no way meant absence of guilt. A good analog for this might be how the Bush administration's intel/foreign policy hawks felt about Saddam's purported nukes.
I really don't believe Obama is the kind of person that would rationalize politicizing intel (or the lack of it) the same way that, say, Dick Cheney and Don Rumsfeld did. I mean, he of all people knows that he was the occupant of the Oval Office in no small part because of how the Bush administration handled the Iraq war. He's also a lawyer. His wife is a lawyer. They know the consequences of breaking laws (this is before the SCOTUS's infamous ruling, mind you, so he makes the assumption that even presidents can be prosecuted for malfeasance after leaving office). In the end, I think Obama's crime was wanting to believe the people he hired and had trusted to senior positions in his White House. He trusted them, and in a way, I think they betrayed his trust.