The most parsimonious explanation — meaning the one with the fewest assumptions — depends on how you weigh two competing factors: physical evidence vs. institutional credibility.
Based on available data, here's a breakdown of the two leading theories:
1. Fire-Induced Collapse (NIST explanation) – "Official story"

Strengths:

Consistent with known physics of thermal expansion and material weakening.

NIST simulated a chain reaction from Column 79 failure, leading to progressive collapse.

Building burned unchecked for ~7 hours, with no firefighting efforts and extensive interior fires.

Internal collapse was not externally visible until the façade dropped — consistent with a sudden structural failure.

Weaknesses:

First and only time a steel-framed high-rise collapsed from fire in a symmetrical, near-free-fall manner.

The explanation requires a very specific failure sequence, including beam dislodgement and multiple cascading failures, all without asymmetrical collapse.

Critics argue that the model used by NIST was never fully released for peer review, limiting transparency.