William Burkitt on Matthew 8:28

We read of few, if any in the Old Testament, that were possessed with evil spirits; but of many in the New Testament. Our Saviour came into the workd to destroy the works of the devil; therefore he suffered Satan to enter some human bodies, to shew his divine power in casting them out.

Note here, 1. That the evil angels by their fall, lost their purity but not their power.

2. That they do no oftener exert their power in doing mischief to the bodies and lives of men, is from the restraining power of God. The devils cannot do all the mischief they would, and they shall not do all they can.