After the end of the cold war, during the Europeanization of the international relations in the region, energy politics played a significant role for Turkish-Russian rapprochement. While energy was the most important factor for Turkey, for Russia it was the perception of the U.S as a threat in Black Sea and Caucasus region. Thus Russian vision to improve relations with Turkey mostly relied on both economic and geopolitical factors.
The Arab Spring, however changed everything in the region along with Turkish-Russian relations.
While Turkey desperately tried to overthrow the Assad regime and supported the opposition groups during the Syrian civil war, Russia and Iran gave a full support to Assad regime.
The tension between Russia and Turkey accelerated when Russia started an aggressive military campaign against ISIS and other opposition groups in Syria and has peaked when a Russian plane was shut down by a Turkish jet last year.
Russia did not respond militarily to Turkey but started an economic embargo and a smear campaign against president Erdogan and his family especially in U.N Security Council. Thus, one of the most important reasons that the President Erdogan to start the rapprochement is based upon primarily to stop Russian efforts in U.N Security Council against Turkey.
Many also believe that closer ties with Russia carries a connotation to blackmail the U.S to get the extradition of Mr. Fethullah Gulen who Erdogan sees as an enemy since the corruption probe in December 17, 2013. Improving ties with Russia, Erdogan also implies that Turkey can leave NATO and start a new strategic alliance with Russia. While it is definitely safe to consider that Russia may want to exploit Turkey's situation to weaken NATO alliance getting Turkey into its orbit.
However, the American policy makers do not view it as a zero-sum game. Instead they see it coherent with their interests in Syria especially combatting the ISIS threat. For the Russian perspective, accepting Turkey's apology and starting bilateral relations would force Turkey to a radical change on its Syrian perspective and engagements.
Even though, NATO considers the Russian aggression in Eastern Europe as a serious threat, it doesn't seem the rapprochement between Turkey and Russia will result in Turkey's departure from NATO.
On the other hand, the closer ties with Russia will not change the Russian perspective on Kurdish YPG which Turkey claims it is linked to PKK. U.S Government considers the Kurds as a strategic ally against ISIS as well. While Russia may request Turkey to take serious steps against ISIS, Turkey is vulnerable to ask the same thing from Russia for YPG.
One of the most important result of the failed coup in Turkey is that Turkish Military is now more vulnerable to the attacks of PKK, considering almost 40 percent of the generals are in jail and thousands of the officers are arrested.
The recent developments in Turkey may have drastic effects on Turkey's Kurdish issue.