Answer:
The Germans had no initial plans for invading Great Britain. Though they had mapped everything out, there still wasn't a plan concrete enough to execute. They were also massively under equipped; they simply didn't have the control of the sea and skies necessarily to launch an attack on the island. Not to mention that the will of the British were incredibly strong, and they definitely weren't going to go down without a hefty fight. Those reasons are mostly why they didn't launch a swift attack on Great Britain.
Step-by-step explanation: