I wonder if he did pose much of a threat in that his presidency created the perfect environment to weaken the US government by creating such a division in the public that nothing said by either side was believed. That crisis of authority is extremely dangerous to any national structure - just read about a similar social upheaval prior to the French, Russian and Chinese revolutions. The incredible political pressure leveled on Trump increased the necessity to find a quick solution to COVID. This plus his pro-business stance made it easy to sell the mRNA vaccine as the only solution to the pandemic.