Symbian folks inside Nokia at the time lived in a reality distortion field. Your experience is not the only instance where the Symbian division inside the company railroaded the Maemo project, which they saw first and foremost as a threat to their jobs and political dominance. As TFA notes, N900 was preceded by N770, N800, and N810 "internet tablets". N810 in particular was basically the same device as N900, but despite having otherwise state of the art wireless communication tech all of them lacked one very crucial component: a mobile data modem. Internet connection was only possible over WiFi (or even RJ45-USB dongle) but not SIM.
The reason for this was of course not technical - the Symbian folks inside Nokia simply managed to convince the executive level management that adding mobile data would turn these devices from PDAs to a smartphones, and it would be very ill-advisable to launch a competing smartphone platform to Symbian.
When Maemo folks finally got a chance to "give us a try" (and I guess management saw with the competition that they needed something more modern), the result was N900. Considering it was meant as a "niche" device its sales exceeded all projections. However, in the grand scheme of things it was just an experiment designed to fail and further cement the dominance of Symbian.
I think Nokia also developed a fully-working tablet around either Maemo or MeeGo. It was literally ready to ship, but was at last minute cancelled before the launch event due to backroom dealing again by the Symbian folks.
It has all been documented in the book "Operation Elop", which paints a pretty good picture about everything that went on behind the scenes during the demise of the once great Nokia: https://asokan.org/operation-elop/ The book is based around absolutely exclusive interviews of people who served in Nokia's board and top executive positions at the time.