It wasn’t so much the lack of SSDs. Vista had much higher memory requirements than XP. At the time, OEMs were still regularly shipping systems with sub-1GB RAM installed. Those OEMs put pressure on Microsoft to change the Vista- Ready certification requirements to include their shitty builds that couldn’t really run Vista.

In addition, dual core machines were only just coming to market, so there were a ton of systems with single core CPUs. Plus, with the changes to several driver models and some of the verification requirements (sound, graphics, needing to provide x64 drivers to get verified) from XP to Vista many vendors decided to EOL their products instead of write new drivers. I know many sound cards were EOL that were literally still on store shelves.