Question

It seemed to me as if nothing would or could ever be known. All that had so long engaged my attention suddenly grew despicable.

Answer 1

I think the first answer is right

Answer 2

Answer:  He no longer enjoys his work.

In this excerpt, the speaker tells us that everything that he had previously been interested in suddenly became horrible to him. It is likely that the work the speaker was engaging in stopped being interesting or enjoyable for him. Moreover, he states that he began to feel as if nothing would or could ever be known. Therefore, it seems that the source of his frustration is that the speaker wanted to find out the truth of something, but now believes that it cannot be known.