The first is that he was born in Italy during Napoleonic rule, meaning that he grew up in milieu of anti-clericalism and irreligion. His large peasant family placed him with an uncle and he was a shepherd. Young Dominic became attracted to the Passionist Order and joined them as a novice in 1814, after restrictions against religious orders were removed.
Secondly, although in England his English language skills were never that strong (which probably gave some the impression he was not that bright), he was a tremendous theologian and scholar for the Passionist order. He was entrusted with greater and greater responsibility.
Thirdly, he received this special call to serve the people of England and received converts. I believe he heard that call because John Henry Newman needed him. As Newman was living in Littlemore after the suppression of the Oxford Movement he was as he said on his deathbed as an Anglican--but he was not yet ready to recover and become a Catholic. The example of Father Barbari, enduring ridicule for his poor English, being stoned in the streets and yet persevering to bring Christ to the people--even leading the first Corpus Christi procession in England since the Reformation--impressed Newman.
Father Dominic worked very hard while in England, establishing churches, preaching and teaching. He suffered a heart attack and died in Reading on August 27, 1849. He is buried in St. Anne's church, St. Helens, Merseyside, alongside Father Ignatius Spencer, an Anglican convert and Passionist, and Elizabeth Prout, another Anglican convert and the foundress of the Institute of the Holy Family.