“There is no other plausible explanation” translates as the occultation of Yemen. Yemen only features as the pounding ground of a vicious Saudi war, de facto supported by Washington and London and conducted with US and UK weapons, which has generated a horrendous humanitarian crisis. So Iran is the culprit, no evidence provided, end of story, even if the “investigation continues.”
Source: Escobar: How Yemen’s Houthis Are Bringing Down A Goliath