How did direct collapsing black holes form so early in the universe?

[wolram]

How are thees black holes formed so early in the universe, weighing millions of suns after only 1 billion years after the big bang?

 

[Chronos]

It is much easier for black holes to grow to great sizes via accretion and mergers under the direct collapse scenario. A DCBH seed is not mass constrained the same way as a star - which cannot exceed a few hundref M-solar under any existing stellar evolution model. They are only limited by the size of initial density fluctuations in the early universe - which could be millions of solar masses. It also bypasses the entire stellar evolution phase giving them more time to bulk up compared to a stellar mass BH. Keep in mind the early universe was much denser than now, so this could be a significant factor.