Did Maxwell Over-Speculate on the Physical Nature of Electromagnetic Waves?

Since James Clerk Maxwell wrote his Treatise in 1873, it has been generally believed that electromagnetic radiation consists of oscillating electric and magnetic fields, perpendicular to each other and in phase, and mutually perpendicular to the direction of propagation. It will now be investigated as to how exactly Maxwell arrived at this perhaps over-simplistic conclusion.

https://www.researchgate.net/publication/348444854_Did_Maxwell_Over-Speculate_on_the_Physical_Nature_of_Electromagnetic_Waves