Actually about 2 million of the most educated people in Russia left when Putin first declared war on Ukraine

why?

Because they were educated enough to see what was coming and didn't want to be a party to the destruction of Ukraine in any way, shape or form. By Leaving Russia early they could vote with their feet and leave just like thousands and thousands more of the common people are doing now and will continue to do ongoing into the future, even if they have to run across the border without border crossings across land in any way that they can into places like Finland and others.