The Finnish parliament will no longer carry Pepsi products as the American soft drink giant continues to support the Russian economy by continuing its operations in the aggressor country, Finnish news outlet Yle reported on Sept. 5, citing the manager of the parliament’s restaurant.
They have a duty to try and maximize the return on investment for their stakeholders. Dumping all of their stock on the market at once would crater the value of those holdings. In the end the only people who would benefit would be those who picked up that stock cheap (probably the Russian Oligarchy). It would also greatly harm the Sovereign fund due to the losses incurred.
Selling off holdings slowly to try and minimize losses for the sovereign fund is the logical move.