Passkeys are new, so people are still unfamiliar with them.
Nobody can put a passkey on your device other than you, because you have to authenticate (prove your identity) before a passkey is created.
You have a Microsoft account - that's how you're able to post here - and a Microsoft account can be signed in with a passkey. In fact, that's a very good idea.
Here's where it starts to get confusing: the technology behind passkeys is standardized, however the industry has not agreed on a standard user interface, so each website does it their own way.
Microsoft (and Google) are particularly aggressive about installing passkeys on devices, perhaps because they're tired of getting so many complaints about stolen accounts.
If you already authenticate to your device in a password-less way, like with a pin or a biometric, then you have already authenticated to your device, which is what a passkey needs in order to work.
So what probably happened is that a passkey for your Microsoft account was installed on your device, either automatically, or because you were confused by a dialog box that Microsoft presented to you. However, with the changes you have made to your system, I can't predict what's happening on your computer now. In future, if you want to delete a passkey stored on your device, Microsoft's supported method is on their website: View and delete passkeys saved in Windows