MS had a much larger market share than Apple does in any product category. They were something like 95% or more of the PC OS market. Apple has, in the US, around 50% of the smartphone market and around 15% of the PC market.

MS also did a lot to curtail competition that Apple hasn't even come close to. Like how they crippled BeOS by threatening OEMs with higher Windows licensing costs (as a low-margin business this would have pushed any OEM prices too high to remain competitive).