KaiOS is in the ultra-low-end smartphone/feature-phone market that Microsoft/Google/Apple don't care about at all.
What's remarkable is that something ill-conceived like "web technology on ultra-low-end devices" actually gained enough traction to get devices on the market.
Like Firefox OS before it, actual KaiOS devices were not well-received, because of poor performance and lack of apps. It's just that nobody really notices because all the buzz is around "real" smartphones.