"It" is acting as a sentence introducer here. "It" and "that" have this functionality where they sometimes just introduce the sentence.
For eg: That the prices are going higher is a concern for all.
Here the fact that prices are going higher is a concern and "That" doesn't have any antecedent as it is just introducing the sentence.
Similarly, It was an honor to meet the president
"It" here can not refer to honor. If we replace it with honor, we get honor was an honor to meet the president and this is definitely not correct.
It is just a sentence introducer here or place filler as some prep companies say.