In the last photo you can tell that it was not the strut that broke first
Curious. Looking at your pictures and the damage. I would have said exactly the opposite. Furthermore, It is a shame that your phots dont have a close up of the broken part of the strut, but from what I can see, it appears to have fractured. If the prop had gone first, I would expect to see more evidence of bending before breaking on the strut.
If I was inspecting this, I would have written it down as a strut failure of the bracket allowing the propshaft to whirl around resulting in the prop hitting the bottom, and with sufficient force to damage the prop blade.
BTW I reckon you are very very lucky not to have lost the boat either by the prop going right through the bottom, or the total failure of the shaft seal.