But they way they promised it was heavily caveated before the election.
The only commitments to spend were funded by cuts elsewhere (assisted places > reduced class sizes) - The main increase was to restore education spending to as much as it was in the past, and only if the economy grew.
If they simply answer yes to 'will you do x', then they end up writing their manifesto via media interviews. The hard-left twitterati and their 'evil Keith' memes are the useful idiots of the right.
It was the same in the 1990s - Blair was a Tory and they're all the same, so why vote for Labour?