Spain was too busy with the Inquisition. Interior programs kept true expansion curtailed in the New World.
Any argument can be made for and against. History is written by the winners. Prior to the invention of photography and audio recording, persons of history only left diaries, journals and letters for the historians to work with.
Either you take that a face value or consider them falsely written. No empirical evidence will ever be 100% for or against. We are left to our own personal thought, suspicions, and theories.
From a conspiracy point of view, this was fallout from when the Templar Knights were overthrown. Royal families were still exercising their authority over the Church keeping the Pope and his representatives away from any power. England, France and Spain were the superpowers with the navies. No king or Queen wanted to be number two in that trio. Ego played a huge part in national direction.
Conspiracy theory: Illuminati placed secret agents in the Courts of the monarchy and in the Holy See of the Vatican keeping them all at each others' throats.