Noted. How sure are they that the bb brought this dimensionality and not something else? How are they sure it is dimensionality that was sprung from the bb, not something different?
Im just curious to know
It does not have to spring from BB, but BB Theory must explain it. It is really so simple, that for me, it was a bit difficult to grasp, at first. Dimension is a quality of Space. But, even that is not enough. Without Matter, there is no way to qualify Space as having dimension. And without Space, only Matter, say, it also would be dimensionless, but a solid.
It is one of the most basic questions, as you point out. In Quntum speak however, it is all resolved. There is no dimension at all, unless we Observe it.
Since we are, at least for now, accounting for 11 dimensions in the widely accepted math, these new ones don't exist. But, when we figure out a way to observe them, they will. Weird. Some want to draw the line at the mircoscope, atomic lengths for the Uncertainty effects. But, there may have been observed macro Effects in history. These are the stuff of legend, perhaps. But, we cannot rule out, that someone managed to create a macro event by Observation alone. A tech so advanced it seems magical. BURN them.
They are locked up as crazy, or worse. And how will we ever know what is possible? We insist that the Reality be defined in a way that "everybody" can accept it, when we know it can't be. Beyond cetain levels like the Planke length and those wave/particle Uncertainty results, we have no idea.