It doesn’t make any sense for a public figure to speak in a place that’s empty. Social networks grow from the ground up, not the other way around. If the population doesn’t like X they should stop using it, and their leaders would move to the platform where they are.

The other way around is self evidently absurd, nobody will change platforms on the basis that a prime minister is publishing some messages there and no politician will spend time talking to nobody when everybody is in a different place.