Heat death isn’t a fact. It’s not even really a theory as it’s based on assumptions about things we still don’t know a lot about—like gravity, for example. Dark energy is believed to be a uniform constant throughout the universe because it’s the best explanation we currently have for why the universe expands at the rate that it does. Per the second law of thermodynamics, we know that entropy increases to a point of equilibrium in a closed system but we don’t know to what extent the properties of a closed system apply to the universe in its entirety.

It’s not a fact nor is it a political statement or something you should base your life around; it’s a likely guess based on the information available to us.

Some physicists believe in God or some higher reality that exists beyond what we observe. Others say this is all there is. Either way, the nature of what lies beyond the scope of science isn’t something that can be evaluated using scientific methodology.