God, someone really doesn't understand polling.
Let's break it down simply.
Let's use 538 because people love to rag on them for "getting it wrong".
On the night of the election, 538 gave Hillary a 71.4% chance of winning versus Trump's 28.6%.
Source.
This doesn't guarantee Hillary a victory because it's a value greater than 50%, it's telling us there is ~3/4 chance she wins, a ~1/4 chance Trump wins. Not that complicated.
If I were to tell someone that there was a 1/4 chance they could win $1,000,000 and a 3/4 chance their worst enemy would win it, I imagine they'd jump at the opportunity. I know I would.
And to Milk_Man, the Russian narrative has come about because of the questionable ties of former Trump campaign members to Russia. Manafort, Stone, Page, Sessions and Flynn all have had contact with/worked for Russian state operatives/affiliated agencies. In November Foreign Minister Sergei Ryabkov told Interfax News (Russian news) that there had been contacts with his team during the campaign.
There is no doubt that Russians, be it state or independent agents, flooded the web with fake news. It's not just targeting the US however, it has targeted France and is now targeting Germany.
There is a lot of questions surrounding these actions, which is why so many people (excluding most House and Senate GOP members) on both sides of the political spectrum want there to be an investigation. A Fox News (yes, I'm using Fox because it's a conservative site which goes to show how big an issue it is) poll during March of 2017 showed that 40% of GOP voters, 90% of Democrats, and 60% of Independents want an investigation into the combination of meddling and collusion.
Who knows what will come of it. If it's nothing, then the Democrats will look foolish. If it's something, well, then there are bigger issues on hand. But the public support is behind it.
People claim there is nothing, but there is a Senate Intelligence Committee who recently subpoaened Flynn and his associates, the FBI which raided a GOP PAC HQ, and ongoing investigations by both the House (which has been stonewalled) and Senate. But given the partisan nature of politics in this day and age, people want an independent investigation.
And now, with the Director of the FBI being fired who was leading the FBI's investigation and Trump telling Lester Holt that his decision was partially influenced by this investigation, there are a lot more questions.