I think there's an unfortunate misconception about the original question of causing gravity in the first place. It's all fine and well to say that energy warps spacetime, which alters the geodesics which is how we observe the 'force' of gravity, but one can equally well ask why it is the case that energy should warp it in the first place. The answer here is that it just does. We could probably dig around in string theory of some equally complicated theory of quantum gravity and tell you about interactions between fields and bosons and other things, but ultimately you can still ask 'well why do they behave like that?'
If you see where I'm going with this, it's that science isn't about asking 'why' questions, but rather we like to answer the 'how' questions. If you ask me how gravity works, I can describe it to you very accurately by simply writing down the Einstein equations. Why do they work? Not sure, but I know they do to a remarkable degree of accuracy. Unfortunately, at some point you simply have to accept axioms about the world or else you're going to be lost in the doldrums of philosophy. When your axioms lead to predictions which contradict experimental evidence, then we revisit them in order to find axioms which will more accurately describe reality -- this is the way theoretical physics progresses.