My wire cage killed my puppy?

My father found this 2 month old american bull dog on the side of the road 1 month ago. She was covered in fleas but never got sick. She got her flea shots and other puppy shots as soon as we got her. We started crate training as soon as we got her because we can not leave her out while we are not home so once we leave for work she gets put up. The cage we have is a metal wire cage that we have had for years for all our dogs with no issue. Yesterday i got home from work and was going to let her out as i do everyday, when i noticed she’s not whining for me to let her out. As i get closer i noticed she isn’t moving at all and her paw is sticking out of the cage. i immediately open it and could feel she was no longer breathing and was cold. I have thought of the situation over and over again since it happened until now. The only likely cause i can think of is she got her foot stuck, tried to get it out but started to freak out when she couldn’t get it out and maybe broke one of her joints and went into shock. She had realeased her bowel and bladder. When i was cleaning her pee it had a blood color to it.

My question is has anyone heard of story’s of wire cages killing there dogs or injuring them? Another would be if anyone can think of anything else that could have caused the death?I am willing to answer any questions needed. What could the blood in the pee be caused by?