“Darius” (6:1) conquered Babylon (5:31) and set up 120 princes. That doesn’t contradict Esther 1:1-3, for that took place 17 years later after they conquered 7 more provinces.
How is “Daniel” alive (6:2)? He refused to be a ruler in Babylon (5:17), knowing the city was about to be conquered and her rulers slain. But the king insisted (5:29). Well, they probably didn’t kill him because they heard he predicted Babylon’s fall and figured his God must God. That’s also why he was the “first” president set over the 120 princes (6:2) so the king would receive none of the financial “damage” kings get when princes steal tax money (cf. Ezra 4:13).
The princes were jealous that he was about to be made ruler over the whole realm, so tried to find a fault in Daniel “concerning the kingdom” (6:4), i.e., in his management of it. But they couldn’t find any fault of any kind, making him a type of Christ. Israel’s rulers tried to find fault with Him because they knew He too was about to be head over the
whole realm of Israel (6:4 cf. Lu. 20:19, 20), but failed (23:13, 14).
Daniel’s also a type of Tribulation saints. They will be rulers in the kingdom (Mt. 5:5), so Antichrist’s followers will try to find fault with them (Ps. 37:11, 12). Psalm 10:49 calls them lions in a den (Ps. 10:4, 9). That’s why Peter tells Tribulation believers to obey the king so they can find fault in them concerning the kingdom (II Pe. 2:12-15). The Spirit will help them be as sinless as Daniel (I Jo. 3:9).
So the princes knew they had to find a way Daniel’s religion broke the law (6:5). That’s what the Lord’s enemies charged Him with too (Lu. 23:1, 2). But Daniel’s religion didn’t break any laws, so they proposed a new law (6:6, 7). Daniel would have to break that law because his law said he had to pray thrice daily (Ps. 55:17). By the way, prohibiting prayer to any God or man (6:7) makes this a type of the Tribulation, when a man will claim to be God.
The king signed the law, making it unchangeable even by the king himself (6:8, 9). This established a state religion, one men had to accept or die, like Rome had for centuries and Antichrist will have. He’s called a lion (I Pe. 5:8) and his “many” antichrist’s (I Jo. 2:18) made up a den of lions. On the cross, the Lord prayed to be saved from the “lion” of the devil (Ps. 22:1, 20), and so will Tribulation Jews.
Daniel refused to stop praying to God because his prayers took the place of the offerings that God’s law said he had to bring (Ps. 141:1, 2), and because while in captivity he was supposed to pray “toward Jerusalem” (I Ki. 8:44-50 cf. Dan. 6:10). His 3 friends weren’t caught praying because Daniel is in his 80s and they were probably dead by then.
Darius was mad at himself because he knew the princes envied Daniel and tricked him into passing the law. He knew Daniel was innocent so tried to save him (6:12-14). That’s a type of how Israel’s rulers envied the Lord and delivered Him to Pilate (Mark 15:10), who knew the Lord was innocent so tried to save Him (Mt. 27:11-26). Since Darius could have no power against Daniel except it were given him of God, he’s a type of God, who anthropomorphically tried to figure a way to save His Son from the lion at the cross. But He too had a law that couldn’t be altered, and it said sin had to be punished. He’d like to save His sons in Israel in the Tribulation too, but they broke His law and will have to be punished.
Darius sent Daniel into the lion’s den with an assurance he’d be delivered (6:15, 16), a type of how God sent Christ to the cross with the same assurance (Pr. 16:10). Being sealed in the lion’s den with a stone was a type of Matthew 27:57-60.
Darius found out Daniel was okay “early in the morning” (Dan. 6:19), picturing how they found out the Lord was okay “early in the morning” (Lu. 24:1, 2). God raised Daniel out of the den because he served God continually (Dan. 6:20), and that’s why God raised Christ out of the tomb too.
Daniel 6:23, 24 proves the lions weren’t drugged or overfed, and typifies what will happen to the unsaved Jews who accused the Lord, and the ones who will accuse Tribulation Jews. Darius knew what Daniel taught in Daniel 2, that God’s kingdom would never end (Dan. 6:25, 26), so if he wasn’t saved then, he was well on his way!