King Nadab - true v. false worship and the irony of God's justice

In 1 Kings 15:25-32, we have the account of King Nadab of the northern kingdom of Israel.  He is Jeroboam's son.  Since Jeroboam apostatized from the true worship of the true God by setting up golden calves to rival the temple in Jerusalem, prophets told him that his dynasty would end. 

Under his son Nadab, the dynasty did end.  Baasha killed Nadab after two years and became the next king of Israel. 

It's interesting that Jeroboam's son bears the same name as a son of Aaron who also was killed instantly when he offered strange fire at the altar in a way that was opposed to what Yahweh commanded.  Both Nadabs prove true the classic Reformed interpretation of God's second commandment to not make graven images to try to worship him.  The classic reformed view is that if a kind of worship is not commanded by God in Scripture, if it has not positive precedent in the Old or New Testaments, then it is to be forbidden. 

God commanded Aaron's sons to offer sacrifices through a kind of fire.  Nadab and Abihu offered a different kind of fire and were killed instantly.  God does not kill other people on the spot who offer a strange kind of worship other than what God commanded, but we must beware that we are not worshiping God the way that the pagans worship their gods. 

The second Nadab is the son of the man who said Israel could worship the true God through images of calves, much like Aaron did when Moses was on Sinai.  God specifically commanded not to worship him through images. 

But here is the irony.  God used Baasha to kill Nadab and end Jeroboam's dynasty, and then Baasha did the same things.  It is up to God to bring judgment by whoever he wants whenever he wants, or to have mercy and save the people from their sins.  But I still can't help thinking why.  Why would God use someone to punish someone else when they do the same things?

Even today, we see political divisions arguing for life when each side demeans life.  Trump says that unborn lives are sacred, and I wholeheartedly agree and that's why I voted for him.  At the same time, foreign families are living in cages at the border.  Then again, the people that speak against having immigrants living in cages at the border are doing nothing about it.  They are only wasting time trying to impeach Trump.  Meanwhile, I vote knowing I can't do anything about the unborn or the immigrants.  I want to find ways to protect all life from conception to natural death.  And I want people to come into the country legally but not be treated as animals while they await legal process. 

I can do nothing but pray and await God to sort things out in his time.  And I also am a hypocrite and don't want to be.  Only by the grace of God go I. 

But ultimately God will bring justice to all people, and he will have mercy by bringing that justice onto Jesus instead of those he saves.  He has mercy on whom he will have mercy.  And both his mercy and justice make no sense at times.