The history of the Lightning makes good reading.
Gething points out in his book 'Sky Guardians', that the design originates as far back as 1949, in response for a high speed research aircraft, but this crystallised into a "quick reaction' interceptor, as by 1953 the threat from high altitude bombers was very real for the UK.
It's short range/endurance was of little importance then as the aircraft was only considered a "stop-gap" (under the direction of Duncan Sandy's White Paper) until
replaced by Surface to Air Missiles.
You know the rest. 'Thinking' changed and that "stop-gap" lasted 31 years. The endurance problem became an issue during this long period, culminating in the F3/F6 designs.