Lots of "intuitive" explanations of the problem shared here, but here's one that works for me.

You pick door A. The hosts says you can either keep that door, or instead pick both doors B & C. If either one of them has the prize you get to keep it.

You opt to switch. The host opens B, which turns out to be a goat, and then opens C.

Regardless of what C contains, it's obvious that switching was the better option.