Death was caused by the fall in the garden of eden. death takes place in man due to the sin nature.
In His wisdom and love at times God will allow a person to be taken, be they young or old, but He sees the future and knows their limitations and abilities -
He loved us enough to make us with free will and not as robots or as some communist leaders would have it.....in the fact that He knew, before the foundations of the world He had already decided to become as flesh and dwell among men and offer His life for us = His Grace carries us through if we exhibit faith in Him.
So God can and does allow death, but He also offered a way to have eternal life, through Jesus - the other choice would be hell.
Sin caused death, both spiritual and physical.... but God , as stated, offered a way out.