Usually people at a company are not allowed to sell stock except during special windows. For people at the very top it’s restricted even further where they need to essentially plan to buy/sell stock well in advance. Essentially there is a huge delay to any stock decisions. So these sell offs were likely decided far in advance and once locked in cannot be changed.

For more details read https://www.investopedia.com/terms/r/rule-10b5-1.asp