Anti Roll Bar Brackets Broken! Powerflex bushes to blaim?

This happened totally unexpectedly. I did not hit a pothole or did anything that would justify the bracket breaking. I suspect though that it snapped due to the extra stiffness of the powerflex bushes I installed on the anti roll bar.

The breaking of the left bracket caused the car to vibrate on uneven road, feel a strong knocking when driving on uneven surfaces/bumps. It was very cheap and easy to replace (around $10 for a pair). For installation, the powerflex bushes installation contains the correct steps.