Any time you hang way more weight on a structure than it was designed to support you're asking for trouble.

Overpowering isn't the only mistake. If power was only an aerodynamic deal, it wouldn't be half the catastropy it is.

What also happens, and is almost universally ignored, is that the airframe wasn't made to support the weight of those larger motors. And it wasn't only not made to carry the weight, but the stress that weight causes when the airframe is dealing with what would have been just a few more Gs.

Most designs are adequate for the expected weight of the design engine. The structure was sized to carry the weight and carry it through the aero stresses.... the G forces too. But put twice the engine size on the nose, and go pull those Gs. And add in the fact that the airframe can now pull even more Gs than originally the structure was designed for......

Heck, think about landing. The airframe isn't being aerodynamically stressed beyond expectations, right. But hit a little hard and what does that do? G forces from shock.... now are outside the envelope.