The dogfighting outside the Death Star troubled Grand Moff Tarkin little. Let Vader toy with the rebels in his own way. He knew the truth. The 'weak spot' was a fake. Any moment now, the rebels would land a 'hit' and learn they had been duped - and then, their base would be obliterated.
Yes, evacuation was not needed. This was a moment of triumph. A moment that called for a snack!
Tarkin placed the bag inside the microwave, activating it...
...Wait, the microwave panel was to the left, this was the self-destruct control panel.
"Oh shit."
And so exploded the first Death Star.