It is not just troopers, it's a lot of IL state employees. Pay being ballooned in the final few years of service is just one of the many reasons the Illinois pension system is in crisis.
My grandpa retired as an IL police officer in his 50s and lived for 30+ more years making 6 figures from his pension and getting 3% or 5% (I forgot) adjustments every year. He probably had the most chill retirement of anybody I've ever known (outside of getting cancer twice). He was making six figures a year living on a lake near Dixon, you do not need six figures in Dixon lol