God uses means to accomplish his ends, and often those means are components of the temporal reality we inhabit. So there must be some sense in which, were Jesus to speak with greater clarity, all things being equal that clarity would be sufficient to break down the barriers of the hard-hearted Pharisee. Then those words from his mouth would be the God-ordained means of doing to them what his words did to Paul on the Damascus Road.
But God in Christ does not have a saving interest in these men. He withholds gospel clarity from them.
Similar concept applicable here, Mt. 11:21, "Woe to you, Chorazin! Woe to you, Bethsaida! For if the mighty works which were done in you had been done in Tyre and Sidon, they would have repented long ago in sackcloth and ashes." But God did not give Tyre and Sidon those works, works which would have done in those cities what the sign of Jonah and his words did in Nineveh. Nineveh repented, but (as Jonah so pitifully raged about) God did not do the more as was necessary for his beloved Israel.
Jesus goes on to say, v23, "And you, Capernaum, who are exalted to heaven, will be brought down to Hades; for if the mighty works which were done in you had been done in Sodom, it would have remained until this day." Imagine, having so hard a heart (living amid the holy nation!) that it's harder than the Sodomites.
