When thiking about Armenian capital my natural instinct is to follow Hayastan footstep and pick Armavir with it's rich mines and large trade connection. However for NON Hayastan the administrative capital is in Shamushat. The Seleucid Satrapy and the Armenian Satrapy title is in Shamushat and Parthian Royal Satrapy is not in Armavir but in Shamushat instead.

Why is that?