Yes, there were commercial, online information services in the 1980s, and some of these included access to an encyclopedia, such as the one published by Grolier. Here’s a directory, from the November 1986 issue of InfoWorld magazine:
https://books.google.com/books?id=jzwEAAAAMBAJ&lpg=PA39&ots=...
These services were relatively expensive, and I’m not sure how many users would have paid the per-minute or per-record charges just for access to text from a general-interest encyclopedia, which at that time, would have been available in print in nearly all libraries and in some classrooms and homes.
Dialog (https://dialog.com/) still exists, and public and academic libraries continue to offer their patrons access to a wide range of subscription-only reference databases.
