When we got our new Outback last September, I took the time to play with all the electric plugs to figure out what the camper could handle. I did the same as you, 2 heaters on the same breaker in the camper, and after a few minutes it popped and both heaters went off, but the television, microwave, etc. still worked. So I finally figured out which plugs to use so we could run 2 heaters without popping anything. Ever since my initial "exercise" in deliberately popping breakers, I've never popped another one since!
It's all a learning curve! But now you know!