Actually, it was fairly stable between 2003-2013. Then the hardcore political stuff began happening, Erdogan won the political fight to become a popular autocrat assuming all power in 2017 by changing the constitution through a referandum then winning the elections - all fairly.

When he got free from any checks and balances he was free to implement his unorthodox ideas on economics. He put his son in law in charge of the economy, things accelerated but he still had some rebels around him and they took the son in law out of the picture, stabilised the economy just before shit hit the fan. Erdogan proceeded getting rid of everyone not supportive of his ideas and that's when stuff actually hit the fan.

BTW, there's uncovered corruption on a scale unheard in history. Seriously, Turks are no longer impressed by sums less than a billion of dollars. A mayor purchasing insurance from his own son for 10 million $ a year is something that will entertain you for a few seconds as an interesting detail, what keeps coming is the mayor spending 1 Billion $ on dinosaur statues.