I'd expect the canal's owners - the Egyption goverment - to conduct a risk analysis: likelihood of such a blockage and the financial impact if it eventuates. In this case even if the likelihood is low the impact is obviously enormous. Lack of imagination?

Anyway, they charge the shipowners for transit. As long as it's cheaper than going round the Cape they can charge what they like. Maybe that's the problem: if they charged enough to mitigate the risk then these big ships wouldn't use it.

Another factor is, who bears the cost of this event? This should keep lawyers in work for years!