Nothing went wrong. You simply do not understand what a certificate fingerprint is. A cert’s fingerprint is a hash / digest / or (to over simply things) a short string of text that uniquely represents the contents of the certificate. There are other things in a certificate other than the cert’s common name/domain name/SAN; one very important information that a certificate contains is the public key. No two certs generated has the same public key pair. Hence no two cert will ever have the exactly same content, and when the contents of the cert are put into a cryptographic hash/digest function to generate the fingerprint; they will produce a different result.
Fingerprint mismatch = not the same cert.
Anyone who has tried generating their own cert will know, even if you generate both certs for the same domain, everytime you generate a new cert their fingerprints will be different, as a different public/private key pair is generated.
Please read up on public key cryptography and cryptographic hash function for further understanding on the subject matter. GRC’s author Steve Gibson has done an excellent audio podcast on those topics: Security now #34 and #35