Kind of weird that California is tied for 3rd on the list but they make it a point to say people are "fleeing" California before mentioning the other top 3.
People have been leaving Illinois and New York for several years now, so it's probably less surprising than California's more recent stagnation and potential decline.
For the most part, in any statistic involving "Total number of people doing X" California is likely to be first.
I don't see hard numbers anywhere, but assuming that the total migration numbers are within spitting distance of proportional to the population, California would also be, if not leading the list, close to the top in terms of total people entering the state as well.
I agree, that is my assumption about why most people talk about the California migration. They are most likely to personally know someone who has migrated out of California(no tech people). I am from Ohio and can think of 5 people off-hand who left California and live here now. I can't think of another state with more than 2 people exiting. Maybe I am biased because of what I read online.