I know it's probably not the exciting political explanation you were wanting, but a lot of it hinged on numbers; the UK uses first past the post, which means it's not the number of votes cast that's important (Labour, after all, got 48.8% of the vote compared to the Tories' 44.3%) but where they're cast. The Tories managed to have just enough votes in enough constituencies to win 48% of the seats to Labour's 47%. The National Liberals had allied themselves with the Conservatives and both parties agreed not to stand against each others in marginal seats, which meant that with their 3% of seats the Tories were able to form a majority in the House of Commons. That even with this alliance less people voted Tory/Nat. Lib. than Labour is a testament to the flaws of FPTP, but I won't get into that... The Labour party actually gained votes from the 1950 election a year prior, but as a result of the collapse of the Liberal vote the Tories were able to get these constituencies.

That said, there were some political factors affecting the election; although the Tory party had (for the most part) accepted the introduction of the welfare state and indeed the nationalisation of some key industries, they were against further nationalisation (something Labour was for) and Churchill promised to put an end to the unpopular rationing measures put in place by Atlee's government after the war. The fact that Churchill still represented a war hero to many people and the Conservative party had a lot of new, energetic cabinet members also may have played a part.

It's actually very interesting to read the parties' manifestos from the election:

.Tory

.Labour