I would argue that had less to do with beliefs and more to do with ability. When we started out, we didn't have the ability to do much outside of our local region. We still conquered what territory we could. Once we became powerful enough to do so, we engaged in the interventionism you referenced earlier. It began with Latin America and expanded throughout the rest of the world eventually.
If the Founders had the firepower that we now have, I can assure you that most of them would not be non-interventionist. I'm not faulting them for that -- it's just that situations somewhat dictate behavior.