From Haydock’s Bible Commentary:
Ver. 8. God hath given them, &c. Not by his working, or acting in them; but by his permission, and by withdrawing his grace in punishment of their obstinacy. (Challoner)
Permitted them (says St. Chrysostom) to fall into the spirit of insensibility. …] We cannot have a better judge of the sense of the word than St. Chrysostom, who tells us, that it signifies a habit of the soul, firmly fixed in evil, and an insensible disposition: as, saith he, persons under a pious compunction are not to be removed from their good resolutions; so the wicked, under a hardened compunction, are nailed, as it were, to vice. And that here this is the true sense, appears by the following words out of Isaias: he hath given them eyes that they should not see, &c. And also out of David, (Psalm lxviii. 23.) let their table be made a snare, &c. We may understand the spiritual food of the word of God, and of the Scriptures; which by the blindness of this people, have served to their great condemnation. …]
Note that our Lord says something similar in Matt 13:
Therefore do I speak to them in parables: because seeing they see not, and hearing they hear not, neither do they understand. And the prophecy of Isaias is fulfilled in them, who saith: By hearing you shall hear, and shall not understand: and seeing you shall see, and shall not perceive. For the heart of this people is grown gross, and with their ears they have been dull of hearing, and their eyes they have shut: lest at any time they should see with their eyes, and hear with their ears, and understand with their heart, and be converted, and I should heal them.