Re: SpaceX Management is to blame, not a broken strut.
The payload survived. It could have landed and been recovered. They are adding the software to do so in the next attempt.
It was also a failure in manufacturing/supply. I suppose sourcing from 3 suppliers can help, as you'll only get 1 in 3 failure rate if a supplier tries to give you sub standard parts.
They have also considered "adding more struts" as an option. So yes, they can and do have failsafes. The previous failures showed they can, when one engine fails the rest can throttle up or the flight path be adjusted (1 deployment on a 2 bus/satellite delivery).