Did the original Monero core team reach out to cryptographers in order to seek review of the original CryptoNote whitepaper? Or did the mathematicians hear about CryptoNote from some other means and become interested in Monero as a result?
I am not sure how the connection was established, but Surae Noether was paid by the then core-team to review the CryptoNote whitepaper (and thus the CryptoNote protocol), and some of the code of Bytecoin, where Monero forked from. From the review of the CryptoNote whitepaper we can read the following:
For full disclosure, I was hired by the Monero (XMR) developers to investigate the CryptoNote protocol and the ByteCoin code base from which Monero has been forked. The folks involved in hiring me have had no involvement in my review process other than answering my technical questions and sending me money occasionally when I ask them politely and show them the annotations I’ve made. They are paying me in Bitcoin, not in any CryptoNote based currency. Yes, I do own and hold CryptoNote currencies.
As far as I know, there is no public information about how the other two members, Shen Noether and Sarang Noether, heard about CryptoNote and/or Monero, and how they joined the Monero Research Lab. This is a likely result of them wanting to stay anonymous and therefore using pseudonyms to publish their papers.
Over the weekend of the 8th and 9th of November 2014, the Monero Research Lab had a closed mini-meetup in Salt Lake City, Utah, USA. In attendance were surae, sarang, and shen, as well as tewinget and fluffypony. A great time was had by all attendees meeting for the first time, and long academic discussions were the order of the day.