Do you expect that he should have simply sat back and let Lincoln invade?
They knew exactly what he was going to do, he had made it clear in speech after speech, it should have been no surprise.
Actually it was intended as a surprise. Lincoln promised Pickens a food-only mission, but sent a fleet of warships with other instructions knowing fully well that the southerners would not let them in the harbor. Beauregard caught word of it all and preempted the thing.
Yet you seem to believe that Davis, knowing all that, fell right into Lincoln's trap.
To the contrary. He preempted it.
"The North made us do it."
If by that you mean defending one's home territory, yes, it was provoked by Lincoln.
So why Sumter? Are you suggesting that the confederacy would have collapsed and died without it?
I think that is a better question for you to be asking yourself. Why Sumter? Are you suggesting that the union had to have a fort in the middle of a foreign harbor hundreds of miles away?
Davis couldn't have waited Lincoln out?
Had he done so Lincoln would have arrived a day later to fight his way in. Acting when he did was the best way to ensure the least casualties from seizing the fort on either side, and it worked as the casualties of the battle were zero.