They got them good good aromatics! The aromatics in onions and garlic are actually sulphur based, this is what makes them potent when cooked and why onions make our eyes water!!
I knew there was a phrase or word for it but I heard a long time ago ... I learned it from my mom who was taught by French Canadian cooks, I also saw it in lots of French Canadian recipes and it was all reinforced when I noticed the same thing with recipes I learned from Italian cooking (from Italian Canadian friends who were descended from northern Italy)
Creole style "Holy Trinity" is onions, bell pepper, and celery. My first big recipe book was by Chef Prudhomme, cooked a lot of things in that book. Almost all of them started out with sauteing those veggies and than making a roux, Cajun napalm.
As a guy who was limited on cookware. Everything ends up in a big ass pot was very appealing.
I always say this to my friends when they say they don't like onions .... I agree with them, onions are terrible if tried to eat them raw. However, if you cut them thinly and fried them with butter (but basically any oil) on low heat for about 10-15 minutes or longer .. you could eat it like a bread topping.
Fry them faster on higher heat to caramelize them and they taste like candy ... fry them with mushrooms and they go fantastic with any meat dish or barbecue.
Nothing in the world of cooking better than frying onions
But saying all that about onions ... they are good eaten raw in the right way ... the Spanish love making cheese and onion sandwiches. I thought it was a terrible idea but it is absolutely amazing. Now I make my grilled cheese sandwiches with very thin sliced onions. But even just a plain cheese sandwich with thin slices of onion is great.
It honestly bugs the fuck out of me how much I hate onions. I'm genuinely mad at all the delicious things I could try or make with them and I have to exclude them. I've tried caramelized, sauteed, fried, deep fried, raw, yellow, red, white, chopped, finely diced, blended, and all sorts of ways. Don't get me wrong, I eat the dish they are in, but somehow I can taste them and it honestly bugs me.
It's crazy to hear people hate this much on mushrooms and I think they are more of an aromatic and flavorful staple than onions.Umami flavor forever!