Why Victorious was modernized before later armored carriers

Why did the Royal Navy modernize Victorious rather than a larger later armored carrier?

Victorious was intended as the test case, but its very high cost used the funds that could have modernized the later ships.

The Royal Navy chose Victorious as the first ship on which to prove the modernization concept. Experience from that work could then guide changes to Indomitable, Implacable, or Indefatigable. In practice, the reconstruction became enormously expensive and absorbed the available funding. The later ships may have offered more space for large aircraft, but the test case demonstrated how costly a deep conversion would be. The decision therefore reflects sequencing and sunk cost rather than a judgment that Victorious was the ideal long-term hull.