That is his money, why we see it as problem?. Maybe he need fresh fund to develop ethereum or new project that can be use to support ethereum in crypto market. Another reason is he want to save his money because crypto market is unpredictable. We don't need take opinion about his money but his doing to keep running ethereum as the second coin after bitcoin.
If that is the case then they could inform the community and say that they need some funds for the development of the coin and they will sell some of their coins and that no one should panic about it, if they did that then no one will be mad since we understand that developing one of the major coins in the market should cost a lot of money.
But the way this was done makes it seem as if he was trying to hide his actions by doing it at the time in which most people are busy with their families and do not have the time to watch the markets and that gives a very bad impression to the potential investors that may want to invest in ethereum.