60k kids have avoided peanut allergies due to 2015 advice, study finds

I wonder why the old advice was being given if it was so wrong? If nobody understood what to do, shouldn't there have been no advice instead of something harmful?

If people are developing allergies to food, isn’t a logical first step to not expose babies to the allergens? It seems logical. It turns out to be exactly backwards.

It would seem logical, until you learn what allergies are. They are the body's immune system overreacting to something that would normally be harmless, and acting as if it's an invading pathogen. Once you learn that, then realizing "hey, expose the body to this thing early on, and the body's immune system will treat it as normal" is a logical step.

If this theory (that early exposure teaches the immune system not to overreact) is right, then another logical consequence would be that kids who play outside in their early years would have fewer pollen allergies than kids who mostly play indoors and are exposed to far less pollen than the outdoors-playing kids. I don't know where to look for studies to prove or disprove that thesis; anyone have any pointers?