Hmm, the wiki says “ Former military analyst Daniel Ellsberg has claimed to have seen highly classified documents indicating that its safe/arm switch was the only one of the six arming devices on the bomb that prevented detonation.”
The linked story says “ Robert McNamara, who’d been Secretary of Defense at the time of the incident, told reporters in 1983, "The bomb’s arming mechanism had six or seven steps to go through to detonate, and it went through all but one.””
Where is your quote from? I can’t find it in the Natgeo article.
That very same wiki. The very next sentence after Daniel Ellsberg quote: "In 2013, information released as a result of a Freedom of Information Act request confirmed that a single switch out of four (not six) prevented detonation."
So, the failsafes worked as intended.
And yes, they should be even more failsafe.