Typically, being too far behind in development in an open position can lead to the opponent having a local superiority great enough to launch a combination.
Not always, though. Each position is individual and concrete... this is what makes chess so hard: no "general rule" is absolute. With the proper Pawn structure... a Scheveningen center duo, for example... you can be appallingly far behind in development and still have a playable game.
Generally speaking, you need a superiority of two pieces to launch a combination. So if the opponent has one defender in the target area, you would need three attackers. This is just a rough rule of thumb, but it usually works. Then you look for tactics... pins, forks, skewers, overloads, decoying and diverting operations, etc.
A few examples:
From an over-the-board tournament in the Canadian Maritimes:
Another over-the-board game:
So in an open position having inferior development leads to the side with inferior development losing material due to their being not enough pieces defending?