Considering Chromebooks barely entered the market only about 4 years back. "In 2015, Chromebooks topped 50 percent of personal computer sales in the U.S. K-12 education market for the first time, with Windows PCs trailing at 22 percent, according to a Futuresource Consulting report." And looking at the chart in the report [1] is even stranger - Chromebooks have basically gone from 16% of yearly device sales to 50% of…
Even though the numbers are pretty misleading, there are a couple interesting things in them. Presumably iOS had almost no market share in K-12 in 2009 (pre-iPad), yet it took 39% share by 2013. Then Chromebooks took that share and more. Maybe once a market gets disrupted there is an opening for another player to re-disrupt it since customers haven't had time to grow too attached.
But the other thing is, I don't think you're seeing a "disruption" of an existing market. In 2009 and before, nobody would ever have conceived of the insanity of buying one computer for every student. I think this is closer to a new market than anything else. Because neither iPads nor Chromebooks really infringe on the sorts of purchases most schools' IT purchases were prior: Computer labs and office PCs, which are likely predominantly still Windows. (And oddly excluded from these numbers.)