You can think of this strategy as simultaneously buying one long put spread with strikes D and B and selling two short put spreads with strikes B and A. Because the long put spread skips over strike C, the distance between its strikes will be twice as wide as the strikes in the short put spread. In other words, if the width from strike D to strike B is 5.00, the width from strike B to strike A will be 2.50.
While a traditional butterfly with puts is often used as a neutral strategy, this strategy is usually run with a slightly bearish directional bias. To reach the sweet spot, the stock price needs to drop a bit.
Selling two short put spreads with half the width of the long put spread usually makes this strategy less expensive to run than a traditional butterfly with puts. The tradeoff is that you’re taking on more risk than you would with a traditional butterfly. If the stock continues to fall below strike B, your profit will decline at an accelerated rate and the trade could become a loser fairly quickly. That’s because you’re short two put spreads, and there’s half as much distance between strike Band strike A (short spreads) as there is between strike D and strike B (long spread).
Ideally, you want the options at strike A and B to expire worthless, while retaining maximum value for the long put at strike D.