It all depends on the dynamics of the collision. Tall SUVs have their Center of Gravity much higher above the ground than the little sedan Yaris does. The higher the CG is from the ground, the less force it takes to roll the object over. The SUV absorbing the energy of the Yaris put enough force into the SUV to push it over, like a lever. I could really get into breaking this down mathematically, but I won't for simplicity's sake. The width of the car (the wheel track) also significantly affects the stability. A narrower wheel track and taller vehicle, like a 1990s Explorer is much more likely to roll over than a short, wide car like a Mustang or Corvette when going around curves, or in a collision. Take a corner in an SUV a little fast, and you'll feel the top wants to go over. Take the same corner in a Mustang too fast, the tires will break free and slide out of the curve long before it tries to roll over. Semi trucks are huge, heavy vehicles, but they have a pretty narrow track compared their height. That's why they get whipped around in the wind and roll over easily. 

The laws of physics reign supreme. As another "Scotty" once put it...

Larger cars are not always safer. That is a myth and it is one we can blame for all the trucks/SUV's we see on the roads today.

Looks like SUV's tires hit precisely against the compact's tires, giving the SUV wheel a big upwards kick.

At the same time, the SUV's front wheels cut hard left, destabilizing it. Combine all that with a high center of mass, and you're in flipsville.

Or as Chuck so succinctly put it, "physics".