Battery Cable problems of the 2016 Ford Mustang

My car was parked after driving around 2 miles and had been off for around 2 hours. When I returned to car, it would not start and gave me a message saying key was required. Dashboard lights, radio, air blower came on but engine would not turnover, just made clicking sound. I thought key fob was problem so tried the spare one. While waiting for husband to bring extra fob I noticed air coming out of bents smelled like sulpher. When spare fob did not fix problem, we checked the battery and found that the positive battery terminal had excessive corrosion and it was so hot that it was bubbling and the teninal bolt had completely corroded and fell off upon touch. Upon inspection, we also saw that the corrosion had also damaged the end of the battery cable. Five days prior my vehichle would not start after driving around 30 minutes and also said "key required" but when I took the fob apart th o look for battery and put it back together my car started on the next try. Other than that incident, there had been no prior warning that anything was wrong with the battery and I had no issues starting my car.