Complex sentence: Pierfrancesco seems to have grown increasingly disaffected, but his death in 1476 prevented any separation; in retrospect, given how Cosimo would steal from Pierfrancesco's estate while raising his two sons, Pierfrancesco would have been wiser to effect such a separation.
Split into simpler sentences: Pierfrancesco seems to have grown increasingly disaffected, but his death in 1476 prevented any separation. In retrospect, given how Cosimo would steal from Pierfrancesco's estate while raising his two sons, Pierfrancesco would have been wiser to effect such a separation.