1. If the pope were of median age for a Cardinal when selected, then about half the popes would still be around when he died. I don't have numbers, but my instinct would be that more senior Cardinals are more likely to be selected pope, which would mean a minority would be appointed by the previous pope at the time of the Conclave.
2. It was only in 1970 that an age-cap was put on Cardinals in the conclave, which significantly increases the power of the previous pope has on his successor; this disqualifies 117 out of 251 Cardinals today.
3. There are certain positions that customarily come along with a cardinality; following this custom diluted the pope's power a bit. Francis did not follow this custom[1]
If you want a discussion of the papal selection, you could do worse than this substack post[2] from a week ago.
Francis was a smart man, and he knew that in order for his policies to continue he would need to ensure a like-minded successor would be elected.