It has a horrendous drag coefficient, worse than a prius (not that they are a the worst car, but they're not sporty). It needs this to cool and feed the engine.
That stubby tail is actually done on purpose because it reduces drag, not increases it as you claim. A lot of aerodynamics are pretty counterintuitive. Look at the big table of drag coefficients here: https://en.m.wikipedia.org/wiki/Automobile_drag_coefficient
For the Bugatti, they probably weren't going for an ultimate low drag coefficients. They need to make sure their giant engine is getting enough air, which leads to lower performing shapes. Related, they also will want a lot of downforce to make sure the car stays on the road at high speeds; to do this they build a relatively non-aerodynamic car.
Just think this through on a systems level. Obviously Toyota's engineers are not idiots and would use whatever aerodynamic effects they would since the entire point of the car is maximizing efficiency. If it was more efficient to have a different shape while still remaining a practical automobiu, it would. The entire design of the Prius revolves around this.
Also stop just googling for wikipedia links then coming back with information you've only just learned. It's ok not to know everything.