Kremlin has always declared that they do not intervene internal affairs of other countries. That's why President of Russian Federation did not call Erdogan.

It was said by Russian analyst Oleg Kuznetsov while talking to Axar.az about why U.S. President congratulated Erdogan with the victory but Putin did not:

"Referendum in Turkey is the internal affair of the country which decides management of the country in the future, nation should decide on it themselves.

In principle, these issues should not be interesting for Putin and Kremlin. It could concern Putin only in that case if the referendum was against international principles and rules.

The context of referendum fits the rules of coexistence and won't affect relations between Russia and Turkey, also won't have the influence on the position of Turkey in the international arena.

There is completely logical and legal question in my mind regarding this: Why Putin should have called Erdogan? It can be accepted as an intervention of internal affairs of a sovereign country. For example call of U.S. President Donald Trump surprised me: What did he want to show and to whom he wanted to show with taking such step? How can he intervene internal affair of Turkey? I think he can't.

If we are talking about empire ambitions of USA and Russia, call of Trump makes empire ambitions of USA obvious, while Putin showed his loyalty and that do not intervene internal affairs of other countries by not calling".