The Bible says when David took a census of Israel, that was Satan’s idea. Joab couldn’t believe David wanted to do such a repulsive thing, and he only helped because he had to. David was conscience-stricken afterward, and believed he had done a very foolish thing and sinned greatly. And God agreed that there would have to be a severe punishment for this evil act.

But the Bible also says that census was God’s idea! David was just doing what God wanted him to do, as he always did, so why would God have a problem with that? There was never any law against taking a census. On the contrary, God had commanded his chosen leaders to take a census of Israel multiple times in the past, and it was not a problem. God had also made laws about how to do it properly, which implies that taking a census was going to be a regular occurrence.

Non-explanation

Maybe the problem was that David wasn’t following those laws, and wasn’t doing it properly? Nope. The Bible doesn’t say that. It says God was angry because he didn’t want the Israelites to be counted at all.