That might be true for tech startups, but many businesses (even "new" ones) go with Microsoft 365 as a default, especially outside of the west coast or NYC.
The market may not yet be 365-sized but as GP mentioned: it's there.
And there are young people arriving at an age to open a business who have never used a Windows computer in their entire life. To them Microsoft is the company that make the virus-infested, slow, computers full of ads they see at their grandparents' house. That cohort ain't buying Windows / buying Office / using Azure.