The expansion of the universe from a singularity cannot be explained as "Spontaneous Expansion/Combustion." If you believe that science supports this please provide a source. The above reference 'spontaneous' does not equate to beginning of the expansion. There was no 'combustion' involved.
WHY do people always resort to what amounts to nit-picking when faced with something that is diametrically opposed to their beliefs?
I could get into much greater detail regarding what the cosmologist have said in regards to universal origins, but I sincerely doubt it will go without additional nit-picking.
Suffice it to say that current big bang theory postulates the "presence" of a singularity, which precipitated the expansion event which itself permitted what is commonly REFERRED to as the big bang to occur......LIKENED TO, but not the same as, an "explosion".
And it ALL happened spontaneously withOUT the aid or assistance of any known external force, or 'triggering' device.
If you fancy yourself as a qualified cosmologist, suppose you explain it to me, so I can understand it better.