What are the dangers exactly? That a once in a century event can disrupt your supply chain? Is that actually a reasonable thing to try to guard against?

Why do you think that a global pandemic is the only thing that can cause disruption? The ship stuck in the Suez canal was not pandemic related, and that kind of issue can happen at any time. What happens if the Suez or Panama canals are not functioning? Panama is already concerned about the water levels available. What about trade relations going to the extreme side and blocks all commerce with a major supplier? What if union dock workers all go on strike?

Thinking that it can never happen again is just wearing blinders

I'm not saying these events can't happen I'm saying they're rare enough that trying to prepare for them is wasteful. As you illustrated there's all sorts of things that can go wrong. Trying to anticipate them all is a fools errand. And if you spend the capital to try to protect against the rare supply chain disruption all your competitors will just roll the dice and save the money and odds are they will come out ahead.