Reasonably, we have no real idea. This person or group is currently unknown just like Satoshi Nakamoto. The text in this Wikipedia article sums up some thoughts in the community about the creator(s) of CryptoNote:
The author of the white paper went by the name Nicolas van Saberhagen,
although like Satoshi Nakamoto (the author of the bitcoin white paper)
that name is likely a pseudonym. Saberhagen's true identity and
location remains unknown. Some have claimed that the real creator is
someone in the bitcoin community. Adam Back, Nick Szabo and even
Satoshi Nakamoto himself have been floated as possible
suspects, but there is little to no evidence actually supporting
those claims.
Stanford Bitcoin Group’s possible involvement in creation of the
CryptoNote protocol has also been discussed. Prior to CryptoNote
cryptocurrency protocol, the domain cryptonote.org hosted an encrypted
message application also named CryptoNote. This application was
developed by the members of the Stanford Bitcoin Group but had not
received wide recognition. This website currently hosts the CryptoNote
technology.
Further reading:
http://web.archive.org/web/20141205173019/http://thebitcoinnews.com/2014/11/24/bytecoin-satoshis-new-project/
http://bytecoiner.org/bytecoin-source-of-origin/
https://medium.com/@AckermanRonald/stanford-wide-gate-steep-steps-ad95cfccca21