Agrippa went from debtor, to exile, to suicidal fugitive, to prisoner in chains, to king of all Judea. His life reads like the plot of a novel that an editor would reject as too implausible.
According to Josephus in Antiquities XVIII, Agrippa was raised in Rome alongside the imperial family. He was charming, extravagant, and catastrophically bad with money. After his mother Bernice died, he burned through his fortune entertaining Caesar's freed-men and fell so deep into debt that he had to flee the capital. Back in Judea, he was so despairing that he considered killing himself. His wife Cypros intervened and wrote to Herodias begging for help.
Agrippa bounced between patrons, borrowing money, offending benefactors, and barely staying ahead of his creditors. He pawned his way back to Rome and managed to charm the emperor Tiberius, but then was overheard expressing enthusiasm for Caligula taking the throne. A freed-man reported the remark. Tiberius had Agrippa thrown in chains. He spent six months in a Roman prison.
Then Tiberius died. Caligula became emperor and immediately freed his old friend. He replaced Agrippa's iron chains with a gold chain of equal weight as a gift and made him king over the territory that had belonged to his uncle Philip. When Agrippa returned to Judea wearing a crown, his sister Herodias was consumed with jealousy. She pressured her husband Antipas to sail to Rome and petition for his own royal title. It backfired spectacularly. Agrippa sent letters accusing Antipas of treason. Caligula stripped Antipas of everything and gave his territories to Agrippa as well.
The man who had been literally one bad afternoon away from taking his own life was now the most powerful Jewish ruler since his grandfather Herod. The entire Herodian domain was reunited under a single king for the first time in a generation.