This press release by NASA: https://www.nasa.gov/feature/the-universe-s-first-type-of-molecule-is-found-at-last/
When the universe was still very young, only a few kinds of atoms existed. Scientists believe that around 100,000 years after the big bang, helium and hydrogen combined to make a molecule called helium hydride for the first time. Helium hydride should be present in some parts of the modern universe, but it has never been detected in space — until now.
Naively I would expect that the first molecule to form would be the $H_2$. A claim that $HeH^+$ was before that should mean that it has larger binding energy that allowed the molecules to withstand more radiation. However, if I check Wikipedia for dissociation energies of these molecules, I see $436\, kJ/mol$ for $H_2$ and $360 \, kJ/mol$ for $HeH^+$.
Additionally, Helium hydride is charged and should interact with lower energy photons that will destabilize the bond due to sheer quantity.
And finally, the temperature mentioned in the article is $4000 K \sim 0.34 eV$ — which is quite below the dissociation energy of molecular Hydrogen ($4.52 eV$). Why the formation of molecules was delayed so much? Is this one of those situations where baryon-to-photon ratio is important and photons overwhelm the baryons?
Could someone please explain this situation?