The Torah of the Avos is the same Torah as today. Part of the answer may lie in the fact that the Avos had a very unique and perceptive ability/intellect (far beyond ours) which could “see” or “experience” different realities.
Let me explain (L’havdil):
We know that ‘white light’ consists of many colors, from red to violet. Those are the colors that we can see. But we all know that there are emissions of light that exist below red (infra-red, etc…) and beyond violet (ultra-violet, etc…) We can’t “see” them, yet, it is all part of the same light.
The Avos had the ability to study ‘beyond’ what our intellect could grasp.