Why Brazil did not match every regional hull

Why was Brazil's wider fleet smaller than Chile's and Argentina's despite its two dreadnoughts?

Because Chile and Argentina chiefly armed against each other, while Brazil often aligned with Chile and sized its fleet for different opponents.

An audience question notes that Brazil possessed fewer cruisers, destroyers, and coast-defense ships than Chile or Argentina apart from its dreadnoughts. Chile and Argentina were primarily building against one another. Brazil's closer alignment with Chile reduced the need to mirror both fleets ship for ship. Its force was sized to defeat other likely opponents and protect its own interests.