Chuck served on active duty in the Royal Air Force and the Royal Navy, 60s and 70s. Next, because the Royal Family are the top patrons of the Royal military and top diplomats in UK—performing some roles similar to our DoD and our State Department—he then received appointments as a patron/overseer of various military groups to prepare him for eventually becoming King and Commander in Chief: Wikipedia says:
Charles's first honorary appointment in the armed forces was as Colonel-in-Chief of the Royal Regiment of Wales in 1969; since then, he has also been installed as Colonel-in-Chief, Colonel, Honorary Air Commodore, Air Commodore-in-Chief, Deputy Colonel-in-Chief, Royal Honorary Colonel, Royal Colonel, and Honorary Commodore of at least 32 military formations throughout the Commonwealth...I don't know the status of those ranks now that he is the Sovereign. One of his first duties after Elizabeth II passed was to reorder appointments. Regardless, male Sovereigns in Europe, even if long retired from active duty, traditionally wear military uniforms due to their national leadership role.Since 2009, Charles [held] the second-highest ranks in all three branches of the Canadian Forces and, [in] 2012, the [late] Queen awarded him the highest honorary rank in all three branches of the British Armed Forces, “to acknowledge his support in her role as Commander-in-Chief”, installing him as Admiral of the Fleet, Field Marshal and Marshal of the Royal Air Force.
I don’t disagree with anything in your post. I just expressed how over the top the uniform plus all the accoutrements seemed to me. He’d need to shed an awful lot of stuff before leading the troops into battle. (I know, I know, he doesn’t actually lead the troops...)