If the singularity was more than a zero-dimensional point; if the start of a Universe had something besides a spherical configuration, gravity might be able to prevent the release of a unified energy field from becoming mass. E=MC2 was Einstein’s most famous formula. As energy is conserved and slows down into mass with the expansion of the Universe while transforming the energy required for continuing expansion in space-time with new acceleration entering about 7 billion years after the first expansion and inflaton during the first second from singularity questions arise about what new quanta are being converted and what the dark or unknown second-phase energy is. It could not be new energy in the Universe since energy and mass are conserved though convertible.
Dark energy may be converting itself into mass, or the configuration of space-time is being distorted by the new conversion of mass into energy, It could be that space-time dimensions at some point run backwards to reverse time and space in part of the Universe quite apart from mass. The dark energy may be left over from the inflaton and Universe expansion is part of the process. Mass is the remainder subtracted from the energy of singularity expansion.
Though energy is not yet mass. Compacted to a singularity it is not yet even energy. It may exist in an unknown state as pure dimensional space. If it existed within a line originally it would be unbound in one dimension and extended so far as its energy allowed. The forces of energy would be unequally bound and unstable. Mass could not form from energy and would have no singular center to return to if it could exist and were somehow to be big-banged and inflated away