Sowhatnow, yes it truly is a mystery but I can explain it away rather than know! I am not a physicist as others will note but this is how it could be spun.
Imagine billions of years ago the simple hydrogen atom (which at the sub-atomic level is only bound-up energy after all) and energy in equilibrium, not created, just there, swirling around space forming pockets of stronger potentialities in one place and weaker in others. Just as there must have been small zones of attraction and repulsion through the polarity differences or charge, there could also be large potentialities. Given cosmic time this could build up to stupendous velocities and charge and without a magic-maker-man, matter could be created, as Mr Einstein has proved.
(corrections always welcome!)
Next question: how did the energy get there?