Is that why diesel has been popular at Le Mans because you can go longer on the same amount = less fuel stops?
No, the gist of it was that there were different rules for petrol and diesel engines.
Basically Diesels win because they’re allowed a much more powerful engines. They’re not inherently more powerful (anyone can see they’re not, just imagine a drag race between a 2.0 NA petrol and diesel, or two turbo charged equivalents at the same boost pressure), but they’re built to a different set of rules regarding boost, capacity, air intake diameter, etc. Which for the last decade have massively favoured diesel.