Conversation so far:
What is a librettist?
A librettist is a writer of a libretto.
What is a libretto?
A libretto is the text used in, or intended for, an extended musical work such as an opera, operetta, masque, oratorio, cantata or musical.
How was Jean-Philippe Rameau's relation with his librettists?
Unlike Jean-Baptiste Lully, who collaborated with Philippe Quinault on almost all his operas, Jean-Philippe Rameau rarely worked with the same librettist twice.
Why didn't Jean-Philippe Rameau work with the same librettists twice?
Jean-Philippe Rameau was highly demanding and bad-tempered, unable to maintain longstanding partnerships with his librettists.
Were any exceptions noted in the article about Jean-Philippe Rameau not working with the same librettists on multiple operas?
Jean-Philippe Rameau didn't work with the same librettists twice with the exception of Louis de Cahusac, who collaborated with him on several operas.

Question: Why was de Cahusac an exception?
Self-contained rewrite: Why was de Cahusac an exception?