The Ukrainian Parliament voted him out of office. He left Kiev under his own volition. He also resigned from office. The corruption and stolen funds evident in his palatial residence along with the killing of 80 people helped to persuade the Parliament, including his own party, to remove him.
And being driven out of town in no way constitutes a resignation, anymore than when the British burned down Washington and the US government had to flee did it mean they had resigned.
Until the proper method for removing him from office has been completely followed he is still the acting commander n chief of the Ukraine armed forces.