Though BK is responsible for ACT happening, responsibility for treating the employees the way they did, lies with HR and its leader at that time, and RT.
But the worst sin of HR is not ACT. It is the way leadership development was made to happen over the last 10-15 years. Result is that the Management & Tech Leadership of such a high tech company is now 90% filled with bozos. Openly, it is said to become a leader you need to network, not execute.