I'm convinced that we'll find out someday that God was a whole lot more involved in our lives - in history per se - than we imagined or noticed. Just because we don't see His interventions, simply because He might prefer to have them remain unseen, doesn't mean they're not there. On the other hand, they are perceivable to the eyes of faith, just as His sign language is all throughout creation, everywhere and every second of the day.
Sometimes we might not intervene because of our lack of faith, or simply because what we would like Him to do is not according to His will. we may think that He's on our side (as both parties in a war usually are), but then the question is: are we on His side?
Yet at the same time, I don't think He's just watching as the Devil plays one foul after another. He just gives him enough leeway to let him dwell in the illusion that he actually stands the slightest chance of winning. Unfortunately, people are very gullible to Satan’s premature rants of victory, and are siding with him or surrendering to him all too quickly. Which, again, is in God's interest, because He doesn't need fair-weather friends, those who'll side with the one who promises to be the winner or greater advantage for themselves.In order to truly be on God's side, one must be willing to temporarily look like the loser, since that's what God has obviously chosen to do Himself, and Jesus is the best example of that.