You do realise that Microsoft didnt buy the ENTIRE Nokia company, just the mobile division. As part of the sale agreement, Nokia (the parent company) agree not to use Nokia branding on future mobile devices for the next 10 years. So in 2024, you could see nokia phones being sold again in shops worldwide.

Microsoft are forced to change the Nokia name to Microsoft Mobile. Marketing people at microsoft are not stupid, they know the value of one of the most recognised name in the world. They just didnt have the option to stick with it. Same thing happened with acer back in the early 00's.

Acer bought the entire Texas Instruments mobile and personal computer department. The name might sound alien to youngsters but Texas Instruments was very big deal back in the 80-90s (my first laptop was a TI, it cost me RM16,000 with docking station). Same thing with Lenovo when they bought IBM computers business. Acer to date still uses Travelmate name and Lenovo still uses Thinkpad and Thinkcenter. So microsoft most likely will still use Lumia name for their phone lineup but they cant use Nokia brand.