But online Office isn’t secure enough for business use. And Chromebooks cater to the low end of the market. Read the ArsTechnica article. Those users are probably less likely to pay for Microsoft 365 than iPad users.
And it isn’t as if Microsoft doesn’t have a fully functional version of Office capable of running on an ARM platform. They have 2, for that matter (macOS and Windows on ARM).
The Ars article is also a touch misleading, because the data it’s using to support its claim actually shows that Chromebooks outsold Macs during 2020. A year when remote schooling became a Thing for no reason whatsoever that I can think of.
Looking at Chromebook sales in more recent years, they seem to have returned to pre-2020 levels, despite the sheer number of Ars commenters proudly proclaiming that the Year Of The Linux Desktop had come at last.