It is actually kind of sad if you know their history.
Back in the day they were competing with Palm, and had Windows CE and Pocket PC 2000. When PocketPC 2002 came out my employer switched over from Palm and I got to rewrite a bunch of tools. They did pretty good for a while with Mobile 2003, and Windows Mobile 5. It knocked Palm down several notches in the mobile market, with Palm losing value and getting bought out in 2005.
The fun thing about that era is that there were phones with PDAs in them, you can go back to "Pocket PC Phone Edition" for that. Each version of Windows Mobile supported running in phones, but they never took off.
The iPod was getting some power and some apps, but I loved that with a single CF card I could have my entire music library on my device; the Axim x51v used the same audio chipset as the iPod of the era coupled with better playback software where you could mix and such. It also offered all kinds of apps making the device useful for the other common tasks of the time like calendar, email, and web over both wifi and bluetooth.
Again you could get phones running WM5 and WM6 with all their apps, and in late 2006 they had 51% of the market. Blackberry had 37%, Palm was 9%, and Symbian at 9%.
Then came the iPhone. At the time I didn't really see the reason for the hype, when it came to processor power, memory, and even 3D graphics the iPhone was less powerful than my Windows 6 phone.
As the numbers came back, iOS rose and WM feel by the same percent; the other companies were flat in market share. By early 2007 Windows Mobile drooped to 42% and iOS was at 11%. By 2008, WM had 29% and iOS 19% and Android had entered at 2%. By 2010 Windows Mobile devices had dropped to 7% market share, Blackberry had dropped to 25%, Palm to 3%, and Symbian at 2%.
Phones running Windows Mobile continued to exist, but that's about it. Three more versions of Windows Mobile, the three editions as Windows Phone, they have never been able to get their market share back anywhere near 2006 levels.