What does Acts 12:22 mean?

Herod Agrippa I is addressing a gathered crowd. According to the ancient historian Josephus (Antiquities 19.8.2 343–361), this was the second morning of the games Agrippa was holding in Caesarea Maritima in honor of Caesar. It's not certain what Tyre and Sidon have to do with this speech (see Acts 12:20). Josephus says he is wearing a silver garment that catches the sun's rays. The people respond, "Be thou merciful to us; for although we have hitherto reverenced thee only as a man, yet shall we henceforth own thee as superior to mortal nature." Luke translates this more directly here in Acts 12:22.

It's not clear if Agrippa is wearing the robe because he likes it or if he's intentionally trying to look like the Phoenician sun god. Since Tyre and Sidon are in Phoenicia this would be a grand insult, but Agrippa has spent his career in Judea and its environs respecting the God of the Jews, protecting the temple and even reading the Law out loud to the people.

So, it's possible Agrippa is not trying to be idolatrous, but he still hesitates. Josephus says Agrippa sees an owl—a harbinger of death—and realizes he has taken praise that is not his and he will die for it. He purportedly tells the people:

"I, whom you call a god, am commanded presently to depart this life; while Providence thus reproves the lying words you just now said to me; and I, who was by you called immortal, am immediately to be hurried away by death. But I am bound to accept of what Providence allots, as it pleases God; for we have by no means lived ill, but in a splendid and happy manner." - Josephus, Antiquities

Five excruciating days later, he is dead of some kind of abdominal infection, his guts eaten by worms (Acts 12:23).

Paul and Barnabas will later prove to be Agrippa's foil. When they heal a lame man in Lystra the people will shout that Barnabas, who is likely older, is the chief deity, Zeus, and Paul, who speaks the most, is the messenger deity, Hermes. The people will even try to sacrifice to them. Barnabas and Paul immediately tear their clothes and reject the identification (Acts 14:8–18).