Remy usually has much better reading comprehension. Dothraki unchecked without Dany. Give it reread you'll get it.
Of course the war is over if Dany is dead, who steps up Varys, the imp, Grey Worm, Missandei. lol
Repeating now, having unchecked leaderless Dothraki, dragons roaming the skies, and leaderless Unsullied chilling in Casterly Rock is much better than having them united under Dany trying to kill Lannisters. The lesser of two evils.
Except your statement was the war would be over. Having unchecked Dorthraki roaming the country raping and pillaging does not mean the war is over. Having Jon Snow as King of the North does not mean the war is over. Having an Unsullied Army at Casterly rock does not mean the war is over.
I will grant you that killing Dany means all these factions would not be united under one leader but they would still exist and they all would have reason to continue the war save for maybe the Unsullied and even then Missandei and Greyworm would probably continue the war if for no other reason than to get revenge for Dany's murder.
Dany didn't plan on using all 3 of them against the Lannisters at KL anyway. The army that was suppose to attack KL was to come from Dorne because per Tyrion's plan they didn't want foreigners ie the Unsullied and Dothraki directly attacking KLs.
So for all we know killing Dany and without any clear leadership results in several armies descending on KLs as whose going to force the Dothraki, Unsullied or anyone else to stick to the plan if they all want a piece of KL and the Lannisters? Dany's restraint based on the advice of Tyrion was the only reason KL and the Lannisters weren't already dead.
Having said that, if you can take Dany out with little risk then by all means do so. But as it stands, he likely had no chance to escape the dragon after killing Dany so he's removing himself and Dany from the game without thoroughly thinking through the potential implications. That's a bad play. You don't sacrifice an important piece in the game in haste. Hence why Tyrion and Bron recognized, it was a fool's gamble.