Because it was widely believed that Clinton was a very good candidate and seemed to possess high approval numbers throughout 2013/2014. Also when she got behind the Obama campaign in 2008, it was widely believed by most that in return for an Undivided party, Hillary was to be a shoe in for the 2016 democrat presidential nominee.
People we're literally begging Hillary to run in 13/14. The media was all upset that Hillary was dragging out her announcement and pretending to not want to run in late 14/early 15. Hillary had sky high approval ratings after her non political 4 years as Secretary of State. There were actual polls posted on the Atlas showing Hillary winning or scarily competitive in AR,LA,WV,KY,MS, and MO.
