But... they came last out of the three main parties, so it is hardly surprising that they weren't able to implement the entire of their manifesto. The conservatives reneged on many of their manifesto pledges too.
I suspect it is more that the conservatives have much stronger support by the media.
It wasn't that we (I was a Lib Dem candidate in the election) promised it in the manifesto; it was that individual MPs made a personal promise to vote against an increase in tuition fees, and then voted for it.
I suspect it is more that the conservatives have much stronger support by the media.