Why weren't Marines chosen for Normandy?

The Pacific theater was made of multiple amphibious actions involving relatively limited numbers of men and material in a somewhat restricted area. The Normandy landings were a major invasion, the success of which, in large part depended on massive infusions of men and material. Then to be followed by numerous major land engagements. The sheer scope of those engagements would have devastated the Marine Corps. On top of the rest of it, you have to divert men and material from the pacific theater to the Atlantic, and then mix the command structure into an already incredibly complex hodge-podge mixture of different allied free forces, resistance units and sundry other "feeders from the trough".
The Pacific landings were sharp limited engagements, after which the Army could land garrison forces while the Marines reconstituted and prepared for the next landing. If memory serves, the tentative plans for the invasion of the Japanese Home Islands called for a major commitment of Army troops for the main landings with the Marine Corps. to be making strategic supporting strikes rather than having our premier amphibious assault troops being ground up in a numbers match.
So to sum it up in a compact bundle, "The Marine Corps. was simply not the proper tool for that particular job."

Quite simply the USMC was committed in total to the Pacific theater of operations where the strategy of island hopping requires their unique training. Save for the one amphibious landing the Normandy assault was going to be an extended ground operation until the war's conclusion in Europe, more suited for the size, scope and location of U.S. Army forces.

They were otherwise indisposed at other island vacation destination locations

Ok here we go from the hip...I have not scrolled any further than this, either. The Marines were not chosen for Normandy because they were just a tad too busy to join the party in the European Theater of Operations because they were fighting the Japanese on the other side of the world in the Pacific Theater of Operations. How did I do? :D

I hope this will answer your question as to why Marines were not used in Normandy

THE MARINE CORPS IN WORLD WAR II

The U. S. Marines Corps was America's amphibious spearhead of World War II. Its mission was to assault and capture enemy-held islands in the Pacific campaigns. At its peak strength in 1945, the Corps had over 485,000 Marines serving on active duty.

The 6 Marine divisions that served in the war fought, bled and died in some of the toughest battles in the long, brutal history of warfare. They won victories across the Pacific against a fanatical enemy, but at a terrible price; nearly 20,000 Marines died in World War II, and more than 67,000 were wounded.

if my history memory serves me well the Marine Corps was busy fighting off a fierce enemy, in the island hopping campaign against the Japanese and I think such a large movement of troops from the Pacific campaign to the European theater would have alerted Hitler that an invasion was coming and it would have basically eliminated the purpose of having the Army do it which was the element of surprise

Japan. Pure and simple, the Marines were busy island hoping their way across the Pacific Theater. While true soldiers trained in amphibious assault would have been a better tool for the invasion of Normandy, they were a necessary tool for pushing the Japanese back in the Pacific.

They were busy in the Pacific Theater...

The Marines were already involved with the landings in the Pacific theater and due to operational tempo, could not spare large units for the landings at Normandy and Anzio. Marine amphib doctrine, however, was utilized for planning the amphibious landings at Normandy and Anzio.

Because the Marines were being deploy on the Pacific front and remove the Marine and stag them off the Coast of Normandy would have alerted the German s.