Why didn't God simply destroy Saul of Tarsus while he was persecuting believers in Acts 9?
God did not destroy Saul because His grace rises to the occasion. Though the sovereign God could have removed him instantly, He chose instead to show the epitome of grace poured out on a sinful man, even one energized by Satan in rebellion against Jesus.
Les teaches that Saul was fervent, sincere, and devout, but he was like a raging bull, putting forth energy to stamp out believing Jews who had trusted Christ as Messiah. If we had been in God's place, we would have simply rubbed him out and put him away. The sovereign God could have removed Saul of Tarsus so he became nothing but a grease spot or a memory. But God's grace rises to the occasion. Les presents this as the epitome, the very high point, of God's grace poured out on a sinful man. In Saul's rebellion, Satan was fostering and energizing him; he was under the Satanic power of opposing and was not working in the will of God, thwarting everything Jesus had tried to do.