There are a number of posssibilities, but limited probabilities. The most obvious one is that there was "something" prior to the Big Bang for which we can not account or measure. As explored in the book compendium, 'The Evolutioning of Creation' - Volumes 1 and 2, the conditions required for a traditional fourth dimensional environment involved a potential stimulus to be. While the first volume is a more difficult read and speaks to the philosophical rationale for an existence from nothingness, the second volume presents the premise that the reality our existence is actually an intrusion upon the previous nature of the universal being (being in the nature of 'to be').
Perhaps this previous nature was an enceinte non-existence, an a priori existence fostering a medium akin to dark matter; Whereupon the convergence of Time and Space for our reality of existence, the previous order of being embraced an anomolous reversal for positive entropy. Within this reversal, temporary chaos ensued in a deceleration of potential energy toward kinetic materialization. Resultant of this medium of dark matter, dark energy seeks to regain order by accelerating and expanding this new universal condition: i.e., all positive entropy transitions from a state of maximum Time and miniumum Space to a state of minimum Time and maximum Space. Via the evolutionary transition, discrete mass of positive density follows the arrow of Time via acceleration from maximum to minimium Time, from chaos to order, in which order represents the eventual decompostion of positive mass density.