After the Assyrian commander besieging Jerusalem intimidates Judah, Hezekiah goes to the temple and sends his officials to Isaiah. He reassures them that the Assyrians will leave without harming them. This happens, and the commander sends a threatening letter before he departs. Hezekiah pleads with God over it, and Isaiah prophesies again that Assyria won't enter. That night, God kills 185,000 in the Assyrian army. The king goes home and is assassinated by his sons.
Hezekiah gets sick and Isaiah says he will die. Hezekiah weeps, and before Isaiah leaves the palace God sends him back to say he will be healed and have 15 more years of life. Hezekiah asks for a sign, and the shadow on his steps reverses itself.
Babylonian emissaries bring gifts to Hezekiah, and he shows them his treasure. Isaiah hears of it and prophesies Judah's fall to Babylon - Hezekiah's own sons will become exiles and eunuchs there. Hezekiah shrugs, since it won't affect him. He dug a tunnel to bring water into the city during siege. [It is there to walk through to this day!]
Manasseh, Hezekiah's son, reigns for 55 years, and undoes all Hezekiah's reforms for God, and worships Canaanite gods. He sacrificed his son to them, and set up an Asherah pole [a phallic symbol] in the temple of God. He shed much innocent blood [child sacrifice to gods endorsed]. Prophets pronounce Judah's doom for this. Amon, Manasseh's son, reigns for two years, is wicked and is assassinated. The people execute his assassins and put his son Josiah on the throne.
How this is about Jesus
He prophesies the siege and overthrow of Jerusalem, too, mentioning an abomination in the temple.
Hezekiah is one of a very short list of men who knew when they were going to die. It didn't help him live any better, it seems. His son born during the extended time is wicked, and he doesn't care much about future generations. All this after his great reforms for the Lord earlier!
21 - Manasseh's sins are much like ours today: sexual indecency and abortion (children sacrificed to gods of pleasure and fertility). Shedding innocent blood like abortion was the trigger that brought on God's judgment.