Russia imposed severe currency controls to protect the Ruble. That meant manufacturers were unable to send money abroad to purchase goods. I am certain that the Russian Government made exceptions for some categories of critically needed goods, but apparently buttons were not deemed critical. The currency controls have been relaxed, but even if clothing manufacturers are allowed to buy buttons, there will be a period of weeks or months before they can arrive in quantity.
Not true. First most of the current control measures are lifted by now, the importers were exempt from start.