What is the primary physical driver accelerating the assembly of high-mass protostars?

A stronger gravitational attraction exerted on the surrounding envelope

The primary mechanism dictating the rapid assembly of massive stars is the enhanced gravitational influence inherent to their larger initial mass. As a dense core begins to collapse within a molecular cloud, a greater initial mass translates directly into a much more intense gravitational pull exerted on the adjacent envelope of gas and dust. This intense gravitational force directly results in a significantly higher accretion rate, meaning the protostar gathers surrounding material at a much greater speed. This faster infall of material drastically shortens the duration needed to accumulate the critical mass required to ignite sustained core hydrogen fusion and settle onto the main sequence.