Twenty years ago, if you met a mashgiach, you assumed he was not smart enough to be a rabbi.
Working in kashrut certification was a low-paying, unprestigious job.
Now it is a power center. It is a money-maker. The RCC has used kosher certification as a battering ram to bring the recalcitrant to bay and to shift Orthodox Judaism in Los Angeles to the right.
How did kashrut certification become so powerful and remunerative?
It was the chumra movement. Orthodox Jews over the past 30 years felt increasing need to distinguish themselves as more religious by taking on showy strictures such as only eating cholov Yisrael (milk milked under the supervision of a mashgiach) and the like. Kashrut certifying agencies rose up to meet this need and to confer prestige on those who abided by them.
Manufacturers and rabbis saw there was a lot of money and power to be had by using, for instance, only potato starch over Passover. There’s no reason you can’t use corn syrup on Passover. It’s a byproduct and byproducts of chametz are not chametz. That’s the halacha. But oh, to be frumer than thou, that is prestige. And there’s a buck in it.