There are a couple of factors we have to focus on regarding these elections results. Normally, ruling parties lose votes in general elections due to blows felled on a ruling administration during its term in power. But what we see now is that, contrary to losing votes, the AKP actually emerged with more votes this time round. The most important reason for this is mistakes made by the opposition parties. The opposition failed to explain to voters, throughout campaigning, what alternative they could provide in contrast to the ruling AKP. Most of the campaigning passed with a kind of "he said-and then I told him....." kind of vocal-warring. It was simply not possible, in this atmosphere, to present voters with any real kind of important projects. The fact that the opposition fell into this kind of trap presented the AKP with an important advantage.
As for Deniz Baykal and the main opposition CHP, I assert that there is one single reason for the fact that the "vote explosion" expected by Baykal for the CHP didn't occur: the mass antipathy felt for Baykal by the voters of Turkey. Another reason too was the fiasco of the unification between Mehmet Agar and Erkan Mumcu.
It could well be though that the aggressive attitude by MHP leader Devlet Bahceli pleased that voter bedrock, allowing the party to transcend the threshhold, although it's also fair to say that Bahceli's stance also did not sit well with the middle level voter, so sick of fights.
In short, we passed through a campaign season that worked best for the ruling AKP, and thus no one should be surprised that we once again see AKP emerge the victor.