The original plan for the new terminal involved a phased demolition of the old terminal. When the pandemic cratered passenger traffic last year with full air traffic recovery uncertain, the airport authority decided on a new plan that called for demolishing the old terminal all at once in order to speed up full construction of the rest of the new terminal by two years and save $300 million on the project. New completion date is scheduled for December 2024 instead of early 2027.
https://www.deseret.com/utah/2020/5/...-save-millions
The increased bus gates are a sign passenger traffic is recovering faster than the airport authority expected.