The commonest reason a fish ignores your lure is that it never saw it.
Fish hold at a depth for reasons — temperature, light, oxygen, where the food is — and a lure running four feet above them may as well be in the car park. A diving lure is simply the tool that gets you down to where they actually are.
The bill is the lure
That clear plastic lip on the front is what makes a crankbait dive. A long bill at a shallow angle digs deep; a short steep one stays up. Everything else — the body, the rattle, the paint — is detail on top of that one fact.
So buy by running depth, not by looks. Two lures covers most water: something in the six-to-eight foot range, and something that will reach twelve to fifteen.
Fish it into things
A diver working properly should occasionally tick the bottom, deflect off a rock, or bump a log. That contact is not a mistake — the deflection is often exactly what triggers a strike, and it is the only reliable way to know you are down where the fish are.
Where it earns its keep
The drop-off. Summer fish sitting deep. Any water where the surface tells you nothing because everything is happening ten feet down. On a shallow weedy pond it is the wrong tool entirely and will spend the afternoon wearing a salad.