[Suicide Junkie]

Perhaps, He has had the defensive operations in progress for some time now.

The defensive points are stored up, and the defense projects get depleted as enemy intel ops are attempted. He could have stored up 10K per turn in defence, and held off your intel ops using those reserves. If you have 4x his intel, you should be able to wear down his defences fairly quickly, but you'll have to keep at it, and the enemy will know you're trying.