What possible motivation or lapse of judgment could account for supporting a chaotic and deadly upheaval of one's own country - a country which has long sought to establish a secular government?
Deadly upheaval in parts of Turkey during the recent election held down turnout in areas that had previously voted heavily for the pro-Kurdish opposition party, and gave Erdogan the chance to show a tough attitude towards security. This swung the result far enough from the previous vote that his AKP could secure a working majority.
The legacy of secularism left by Ataturk is being steadily unpicked. Don't forget the AKP is an openly Islamist party, which means that it sees Islamic principles guiding and informing the administration of the state. Erdogan's big project is to get a sufficient majority to pass constitutional reforms that will turn the presidency from a European-style figurehead into a US-style executive, just another stop along his "bus ride" of democracy: "once I get to my stop, I'm getting off", as he allegedly once said to the King of Jordan. His even bigger project is the restoration of Turkey's role as a leading Sunni power in the Middle East, hence their involvement in funding Islamist rebels in Libya and Syria - Neo-Ottomanism, if you like.