In two words - Council Tax.
The Conservatives are currently blaming "the national situation" and "national policies" and, of course, the County Conservatives did nothing wrong! But they did. Cambs Conservatives didn't institute the Council Tax freeze after year 1. That is not just the County Council. Conservative run District Councils, The Police and The Fire Authority all ignored the Council Tax freeze and the funding that came with this Conservative pledge.
Ignoring this pledge gave UKIP and the Liberal Democrats a cause to run with. Campaigning on keeping council tax down, UKIP ran riot in areas where they campaigned. The Liberal Democrats held onto their share of the vote to win in some areas.
Whilst UKIP did well, the Independents did well winning in Histon, St Neots and in Cambridge. They took two seats from the LD's and two seats from the Conservatives.
Labour did well in Cambridge by taking seats from the Lib Dems. But the Lib Dems held on to some of their seats.
The maxim seems to be ignore your own parties policies at your peril. The trouble is the Conservatives have yet to come to terms with not Freezing Council Tax. When they do they will realise they were wrong and not the electorate.