Why three smaller carriers could beat two larger ones

Why were three smaller Courageous-class carriers preferable to two larger Lexington- or Akagi-scale ships?

Three hulls could operate in three separate locations. That geographical coverage was particularly valuable to the Royal Navy's worldwide commitments.

The Royal Navy needed carriers in several places at once, giving three available hulls an advantage over two larger ships. An illustrative comparison assigns 75 aircraft to each of two large carriers and 50 to each of three smaller carriers. Both arrangements provide 150 aircraft in total, but only the latter can divide them between three separate locations. Those figures are examples rather than recalled air-group complements. The preference follows Britain's need for geographical coverage and does not imply that smaller carriers are always preferable.