How were astroparticles created?
Condensation of energy into particles.
We really don’t know the precise mechanism, and may not even have all of the actual particles identified yet. But we know that the “Big Bang” was initially energetic, not massive (if that's how it happened).
As Einstein’s equation shows the connection between mass and energy, the released energy “collapsed” (entropy at work already) to form the sub-atomic particles and all of the fermions, bosons, gluons, quarks and whatever else is out there. They in turn formed the protons, electrons and neutrons that went into the making of all of the elements.