I think that the conclusion that I can draw in regards to him helping Hilary is that he endorsed her. The words of a former US President would likely make Hilary look really good in the limelight. Which is what happened. Since Obama was fond of her and publicly endorsed her, people thought she'd be a good choice in terms of Obama's judgement.
It wasn't enough. With some groups he was an asset. With other groups, he was a liability.
It is hard to make a general statement. The reason she didn't get in is that she didn't carry enough of the electoral college seats as she needed to. She won the popular vote by something like 3 million votes, but where she won, the electoral college didn't have enough seats to get her elected. Lately the democrats have had a problem with winning the states that were swing states and could go either way. Their support is overwhelming in some places but not spread out enough to matter.
The problem was not with Obama. The problem was with the electoral college.
