Why? Partly for his education, partly because of his parents’ ambition, and also perhaps partly out of guilt.
Then, when he went to college, the young man rejected the plans of his rich, ambitious parents and joined a new religious group of panhandlers.
His parents had him kidnapped and attempted to "deprogram" him. After a couple of years, they gave up. He went back to college and his religious "family" of beggars.
He eventually got a teaching position and his entire life became devoted to teaching, writing, and praying.
Then suddenly, one day in his late forties, he gave up everything except prayer. He died the next year.
In his relatively short life, however, the little rich boy turned beggar and teacher had already made quite a name for himself.
In his short life, Kings and Popes had sought his advice, so great was his reputation for wisdom.
Even after his short life, religious orders fought over his body, so great was his reputation for holiness.
The body of Saint Thomas Aquinas, the Angelic Doctor, perhaps the greatest of all Christian theologians and philosophers, was finally interred in a church belonging to his fellow Dominicans on this very day
in 1369, 94 years after his death and 42 years after his canonization.(from a previous post)