Transmission and axle

We have a 1995 Toyota Celica GT automatic transmission with 115,000 miles. We took the car into a shop because it had a bad CV Boot. We were told that they needed to replace the axles because that it is easier to replace. After the shop replaced the front axles with after market rebuilt axles, they returned the car. The following day the axle broke after making a turn in a parking lot. It lost total ability to shift the transmission. The car was towed back to the shop. The axle they had just installed broke. We were told that the axle broke into many pieces and they had to pick them out where it connects to the transmission. They then followed by replacing it with the same type of axle for a second time. After driving it, the second axle broke. They notified us that they would have a transmission guy come and look at it. He told them that the transmission needed to be replaced for approximately $2000. The shop that has done the work said the problem was pre-existing when we brought it into their shop. We, along with a few mechanics that we have talked with, think the problem was more likely caused by the first axle they installed. Either the axle was installed incorrectly or it was bad/incorrect part and caused the connection into the transmission to break. The car has shown zero transmission issues prior to having the axles replaced. It has always shifted very smoothly and ran very well. What do you think would have caused this problem?