Even if he did so, prices will fall, his wealth will shrink, this time he has two way to go, The first is that they buy at a very low price, but the reputation of the money has been damaged, restoring credibility requires expensive costs, and the people can hardly trust him anymore, so he does not do so. Second, he does not want to own the coin, the sell-off makes the price of money fall, and the position of his major shareholder will be replaced by others, so he will not do so.
What do you think?
Being a major shareholder is a tricky one. As you said, start selling and you would loose significant amounts if there are limited buyers. Start buying and you could increase your wealth if there are enough sellers keeping the price low and an outlook of an increase in demand.
It is not in the interest of major shareholders to damage the coin in general. However what they will try is trying to put thier invested money to good use by trying to trade against market trends and gather even more wealth. That is why you are seeing the high volumes.
I think it is important that the coin show their shareholders it has potential and ideally provide shareholders with opportunities to invest creating a higher market value for the coin. Just my two cents.