The "ideal" US carrier design had already been developed pre-WW2, but due to Washington Treaty tonnage limitations this would have resulted in an awkward 2.5 carriers. The USN opted for less tonnage and more hulls, yielding the Ranger design which massed about half the ideal displacement.
Thus Ranger was going to have 4 sister ships but had issues; the Yorktown design was better so 2 of those were built and then Wasp sort of cobbled together to fill up the remaining allowed tons.
Once the Treaty was done away with and war foreseeable, Hornet was built while the "ideal carrier" design finalised in the form of the Essex class.
What you state here is correct for pre-war, and US carriers with unarmored (wooden) flight decks...when designing the
Midway-class, the requirements were to armor her flight decks similar to the way that many of the British flight decks were (although the "strength deck" would remain the hanger deck with the flight deck built on top...it was not until the
Farragut-class carriers that the "strength deck" became the flight deck on US carriers)...but they wanted to maintain the 100+ aircraft capacity and 30+ knot top speed while doing so...
Note: British carriers usually had aircraft capacities of around 50 aircraft or less (hanger capacity) because of the mass of the armor vs. requirement to keep high speed on a relatively "moderate" tonnage...some of their carriers managed greater aircraft capacities (around 80 aircraft) by having double hangers (often with shorter hanger heights, which limited their use after the war during the jet age), and/or by means of deck-parking aircraft...
Trying to keep up the hanger capacity while armoring the flight deck and maintaining the 30+ knot top speed resulted in needed to increase the size of the engines, which led to a larger ship, which led to more mass being devoted to armor, which led to a reduction in speed, which led to larger engines, which led to...and so on, until a compromise was reached around 45,000 tons...
For comparison, 45,000 tons displacement is around twice the displacement of the
Yorktown-class and a little more than the
Lexington-class when deep-loaded, and roughly half again the displacement of an
Essex-class carrier...when compared to the British carriers, the 4 ship
Illustrious-class were roughly the same size as the
Yorktown's, while the followup 2 ship
Implacable-class carriers were roughly the size of the
Essex's...the earlier
HMS Ark Royal was built as a single ship class with tall double hangers, and no flight deck, and therefore displaced around the same as the
Illustrious-class carriers, but with half again to double the aircraft capacity (which goes to show you what it cost these types of ships to armor the flight decks)...the
Courageous-class carriers were older ships converted from "Large Light Cruisers", and displaced about the same as
HMS Ark Royal...and we'll leave out the various light fleet carriers of each country (
Independence and
Saipan-classes for the US, and the
Colossus ,
Majestic, and
Centaur-classes for the United Kingdom that were mostly completed after the war was completed...at least on those ships that were built to completion)...
Ruger
