Is it possible for this to happen if they crowned the ball? Hope the term "crowned the ball" makes sense.
Crane speak for that is "two blocking", basically running the block into the boom tip. Typically if that happens, you either pull the ball through the sheeve keeper pins, and it ends up laying 30' behind you on the ground with 100' of cable around it. Or it folds the jib or boom over backwards, which is easier to do if you have block hitting the boom tip, it won't pull through keepers like a ball will.
In this situation where the boom falls away from the crane, there's a couple scenarios.
1- the weight of the boom with load on, driving away or toward the tower, tips the boom sideways, side loads the jib, and it crumples over, that "load" of jib and blade shock loads the side loaded main boom, busts its pendant lines or welds, and it all comes a falling down. The folded up jib on the end of main kind of leads me to this, as well as the busted off house lock pin tells me he was leaning to the side pretty good.
2 pulling ahead or back, front end got light, and the operator decided better to let the boom hit the ground than to stand the crane on its back bumper and he pulled the dogs and let her free fall. House lock could have broke from the bind the tower put on the boom to the side, when the boom hit the tower.
3 kind of similar to #2, may have not had the boom winch dogs in , and smoked the boom winch brake and then couldn't get it stopped. Boom hits tower, wedges it to the side and breaks off the house lock pin.
#4 Pendant line cable or swedge break, or jib pendant, or boom winch line cable failure , or a pin not secured properly, welds popped loose from a broken chord and the extra side load was too much for it, or any one of another million things that made someone have a no good horrible very bad day. Just hope everyone got to go home.