Why would Medici give their money away

Giovanni di Bicci de' Medici had a son name cosimo who was the richest man in florence and he was very interested in politics and spent large sums of his wealth in to reshape florence politiccs and was nicknamed father of his country. this obsession with politics grew until the most powerfull and wealthy medici lorenzo the magnificent who spent so much time and money on politics that their bank started to decay.