It is common for amusement parks to update their ride operations procedures and safety protocols over time.
One possibility is that the operator booth has been moved to a different location, or that the operator is now stationed elsewhere on the ride platform where they have a better view of the ride and riders. Alternatively, it's possible that the operator is now monitoring the ride from a control room elsewhere in the park, which is increasingly common with modern ride technology.
Another possibility is that the operator is still in the booth, but is less visible due to changes in lighting or camera angles. It's also possible that the video footage you've seen was taken during a quiet period at the park, when fewer operators are needed to run the ride.
Overall, without more information or context, it's difficult to say for certain why the operator booth on Mindbender appears to be unoccupied in recent years.