Why was D-Day successful?

Transcript
An extract from the log of a RAF squadron involved in D-Day

Catalogue ref: AIR 27/1879

Extract a

[07:00 TO 08:15]
Today was the "Big Day". In conjunction with the landings of Allied Forces on the northern coast of France, our squadron attacked a number of gun positions just behind the proposed beachhead at Courseulles. This squadron, led by S[quadron]/L[eader] Norsworthy, dropped 24 x 1,000lb bombs in direct support of the Assault landings of the Third Canadian Division. Red Flight struck at one German Battery position, while Blue flight struck at another one only a short distance away. When the bombs struck, both batteries were believed to be "a long distance removed". The actual bombing attacks were made through billowing clouds of smoke and corruption to the tune of an intense sea to land bombardment by heavy naval guns. Tanks were observed landing on the beach and aircraft of all descriptions were present in every corner of the sky. No resistance appeared to be offered to the invaders in these early stages of the attack. All our aircraft returned safely.
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Extract b

[19:45 TO 21:00]
Briefed to search for enemy Armoured vehicles near Caen. F/L Dadson led the squadron unexpectedly over a large north bound armoured column just south of Caen, in France. The columns believed to be a part of the 21st Panzer Division en route to assemble near Caen. The squadron attacked the column with 500 lb bombs and cannon inflicting heavy damage on a score of vehicles. Bombs were dropped over various parts of the column on individual attacks. None of our aircraft were damaged. All returned safely.
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