Some points to consider about early black hole formation:
- Since the universe has been expanding in a monotonic fashion, the density of the universe has been decreasing in a monotonic fashion. This means that conditions may have been sufficiently different billions of years ago, with a greater total mass density, and a lot less mass locked up in black holes, to the point that direct collapse black holes would have been far more plausible, or perhaps even other mechanisms that would be impossible today.
- Theories that involve such phenomena as dark energy or even dark fluid* generally show the expansive forces at large scales to be increasing, meaning counter-gravitational “forces” have gotten larger over time. Depending on how and why they scale the way they do, and if these forces have been monotonically increasing in magnitude since the Big Bang, then it means counter-gravitational forces were smaller in the past, which would be yet another way direct collapse black holes could have formed, or again, that other mechanisms could have led to this.
Anyway, it is interesting to see the starburst theory being cast into doubt. I agree it seems unlikely, unless, by some of the same aforementioned mechanisms, starbursts were able to form much faster in ancient times than today. It would have had to be so fast, and with the following collapse so fast, that none of the stars formed were able to go supernova and disrupt the pristine galactic medium that was observed alongside these supermassive black holes in ancient galaxies.
*Ethan Siegel, you should do a piece on dark fluid. It’s an interesting theory that deserves some science communication treatment.