IIRC Noikia conducted some internal research...
And came to the conclusion that Symbian was ultimately deprecated, & that a sucessor would be needed LT.
Hence the birth of the Maemo project....
But yes, originally they did focus on a form-factor that was quite a bit more differentiated.

It's been discussed dozens of times, but in a nutshell they never treated Maemo seriously enough.

Symbian was seen as the "Golden Goose"....
And when they finally started to treat it with at least equal focus, it was way too late to deliver in a timely manner.
Everyone likes to say it was the Intel tie-up that slowed things down drastically.
But a harder focus on Maemo+Qt far too late, was a much bigger factor. Arii (former tech lead) confirmed that recently.