What are you referring to exactly, US copyright law or earlier laws from other countries? US Copyright law from the beginning (1790) was written in part to preserve the economic property rights of authors and publishers. Part of the point always has been protection of profit. [1] [2]. Initially it only applied to books, not to art. You can’t really separate the granting of a limited-time monopoly over a work from the promotion of new creative works, they go hand in hand, to say economic protection was never the point is not accurate.
‘In 1783 several authors' petitions persuaded the Continental Congress "that nothing is more properly a man's own than the fruit of his study, and that the protection and security of literary property would greatly tend to encourage genius and to promote useful discoveries."’ [2]
The earlier British Statue of Anne says similarly: “Whereas Printers, Booksellers, and other Persons, have of late frequently taken the Liberty of Printing, Reprinting, and Publishing, or causing to be Printed, Reprinted, and Published Books, and other Writings, without the Consent of the Authors or Proprietors of such Books and Writings, to their very great Detriment, and too often to the Ruin of them and their Families: For Preventing therefore such Practices for the future, and for the Encouragement of Learned Men to Compose and Write useful Books; May it please Your Majesty, that it may be Enacted” [3]
Note that both quotes reference economic protection as the first reason, and promotion of creativity second.
[1] https://www.copyright.gov/timeline/timeline_18th_century.htm...