Why wouldn't a faster machine with more RAM be a multitasking machine? (Obviously without extras you are limited regarding security etc, but plenty early multitasking machines didn't have that)
Not in the sense we usually mean nowadays, but assigning pages to processes and switching between them, with a small non-paged segment for general data/code lets you build multitasking systems. E.g. I believe early multiuser BBSes ran on systems like that.
There were tools that added multitasking to the C64, such as e.g. BASIC Lightning that let you run multiple BASIC "threads" + sprite animations at the same time.
It's easy to write a scheduler for a 6502 as there's so little to save, though you'll need to be very careful about stack usage, and you might do better with a specialised scheduler (e.g. for C64 BASIC) as a lot of code you might want to run may store additional state in fixed locations.
Why wouldn't a faster machine with more RAM be a multitasking machine? (Obviously without extras you are limited regarding security etc, but plenty early multitasking machines didn't have that)