No, in the very early universe, prior to electroweak symmetry breaking, there were no photons at all. Before that transition and up to GUT energies even closer to the Big Bang there would be SU(2) W_{1,2,3} massless particles and the U(1) B gauge boson instead. After the transition these electroweak particles combine into photons and the W and Z bosons. Wikipedia is pretty technical about this : https://en.wikipedia.org/wiki/Electroweak_interaction#Lagran...

There is experimental support for the electroweak transition at the LHC at CERN and Lep. LISA (https://lisamission.org), when and if it happens, will also gather more evidence for and against the electroweak transition at cosmological scales, with somewhat less clear-cut (but still highly supportive) evidence becoming ever more available through indirect tests in the interim.

The CMB photons are almost wholly from the recombination epoch at which entirely ionized atomic nuclei -- mostly single protons but other things up to Beryllium-9 -- first became electrically bound to free electrons. The neutralization of these particles releases photons. In the case of Hydrogen-1 + one electron, the emitted photon is principally at Lyman-alpha (Lya) frequencies. Because of the relative abundance of this pairing during recombination, the Lya spectral lines dominate the CMB.

Redshifting preserves the (relative) structure of the Lya lines, and one result of the expanding post-recombination cosmos is that later absorbers (dust, gas) and emitters (neutral hydrogen excited by quasars and so on) produce Lya line structures that are shifted red to different degrees.

The CMB is the reddest Lya structure, although it is smeared into a (differential of) a blackbody spectrum by Thompson scattering, and kinematic effects make it very nearly uniform (correcting for proper motion) in every direction.

Between the end of the electroweak transition and the start of recombination, there were still many photons. These scattered off the electrically charged free electrons, nuclei, and protons, and it is extremely unlikely that there would have been a spectral structure if that light were measured because of the random lengths of photon free paths. As scattering fell off thanks to a combination of expansion (increasing the distances between charged particles) and neutralization (electrically neutral objects don't cause a relevant photon scattering) the photon mean free path became cosmologically long, terminating the randomization of the momenta of photons. Instead of being boosted up or down by process like (Inverse) Compton Scattering, photons emitted by transitions of free particles to bound systems at lower energy states remained at the emission wavelength subject to redshift from the metric expansion of space.

Cosmologists work with a set of points at the time when photons that were essentially freed from scattering around the time of recombination are now reaching us, and call that the surface of last scattering. The surface of last scattering has a cosmological redshift of z ~ 1100, which places it at about 380 thousand years after the Hot Big Bang.

Additionaly, we have several lines of indirect evidence for the Cosmic Neutrino Background, which was emitted more than 379 thousand years earlier than the surface of last scattering, and long-wavelength gravitational radiation detectors on constellations of spacecraft are planned that will probe gravitational waves that are even older than those relic neutrinos. Among the evidence is structural detail in the Cosmic Microwave Background that is sensitive to the density and varieties (in particular rest masses) of the extremely early Cosmic Neutrinos, because they interact both gravitationally and through chiral currents with the various early pre-electromagnetism plasmas.

So the stress-energy in the cosmos was quite busy evolving well before the Cosmic Microwave Background, generating actual observables (and many reasonably-theorized observables that we just can't probe reliably today). There were several different "plasmas" between the hot big bang and the recombination era, each with very different degrees of freedom, and successively much colder temperatures. Moreover, there were lots of plasmas after the surface of last scattering, for example during "first light" as very bright UV sources reionized neutral hydrogen.

I am therefore with other commenters in this thread: we don't see the big bang happening because we can't directly detect anything before the surface of last scattering, mainly because the scattering thoroughly randomized light-borne observation prior to that, secondarily because we can't detect extremely redshifted neutrinos (we have trouble enough detecting neutrinos from fission reactors we have built on Earth, or solar neutrinos, which have not been redshifted to very low energies), and tertiarily because we haven't yet built big enough networks of gravitational wave detectors. What we do see is relatively late in the pre-stellar history of the universe : it had expanded and cooled enormously by then.

Analogies between the early universe and chemical or even nuclear explosions are generally pretty misleading.