It is pretty same on every other sites and not just with stake, on almost all website i know of, including gambling casinos, crypto currency exchanges, social media platforms, what ever the site is, you can easily create new accounts , all that is required is just a new email address, and username, and a new phone number if the site is one that tried to verify users through their phone number.
This is one of the benefits of KYC, it helps prevent multi accounting, only thing is that this does not benefit the user, but the casinos alone.
Yes. But, at the same time, KYC verification is no magic bullet either, and sometimes even KYC is not enough to stop the bad people from creating multiple accounts on gambling platforms. Almost anything that is digital can be forged very easily, including personal identification documents. Any document can be manipulated or hacked and it is very much possible that people impersonate other people.