Huh? Ships have been continually getting larger. https://en.wikipedia.org/wiki/List_of_largest_container_ship...
It was only proven how big was too big once a few ultra-large had been built, and the point of diminishing returns had been exceeded enough so accurate math could finally be accomplished.
Routine commercial operation has been scaled back decades ago to less than the max.
Less than the max that is physically possible, focused now more accurately on better returns.