Apple has no way of knowing that email address is actually yours. It could be somebody else had that email address, created an Apple Account with it, then abandoned both items. The service provider unfortunately made the email address available to you too soon after it was abandoned by the original owner. The Apple Account created with that address belongs to the original user. Even if they delete the Apple Account, there is still a wait time.
From: How to delete your Apple Account - Apple Support
“Can I use the primary email address for my deleted Apple Account to create a new Apple Account or with another existing Apple Account?
No, once your Apple Account is deleted, you can’t use the email address that you used with it to create a new Apple Account for as long as Apple retains the one-way hash of the email address. For third-party (non-Apple) domain accounts, the one-way hash is deleted after six years. For other accounts, this is retained according to Apple's retention policy, which is reviewed regularly. In addition, you can’t use that email address with another existing Apple Account except as a rescue email. Also, if your primary Apple Account email address is with a Custom Email Domain, it can never be reused to create an Apple Account after your Apple Account is deleted, even if the domain ownership changes.”
Legal - iCloud - Apple
VII. B "In addition, Apple may terminate your Account upon 30 days’ prior notice via email to the address associated with your Account if (a) your Account has been inactive for one (1) year; or (b) there is a general discontinuance of the Service or any part thereof."
So even though the email address is now yours, even if the original owner abandoned the Apple Account used with that address, Apple will wait at least a year before doing anything, then 6 years before letting an account be created with that address.