Windows as a software package would have never been affordable to individuals or local-level orgs in countries like India and Bangladesh (especially in the 2000's) that are now powerhouses of IT. Same for many SE Asian, Eastern European, African and LatinoAmerican countries as well.
Had the OS been too difficult to pirate, educators and local institutions in these countries would have certainly shifted to Linux and the like. The fact that Windows could be pirated easily is the main factor that led to its ubiquity and allowed it to become a household name. Its rapid popularity in the '00s and early '10s cemented its status as the PC operating system. It is probably the same for Microsoft Office as well (it is still a part of many schools' standard curricula).
The fact that Windows still remains pirateable to this day is perhaps intentional on Microsoft's part.
For private individuals and small institutions, yes, they would definitely use linux if windows was 100% impossible to pirate.
For corporations and bigger institutions, no, they would 100% continue to use windows just because of the control they can have on their devices, group policies, single sign on, and so on. It's possible to do that on Linux, but not as easily. They're already paying 15 dollars / month to microsoft just for AAD/entra/[whatever they call it this week] or even more to have office integrated with that and $200 for a permanent license for a single PC is a drop in the bucket