There's now enough meaty bits laying around to figure out the recipe of the sausage they're making with Soleimani.
To wit:
Trump claimed removing him would stop a war. After his removal, they immediately removed the leadership of several powerful militias that were aligned with Solemani.
Soleimani was, prior to his death, one of the most popular men in Iran - essentially their version of Captain America.
The man had, over the years, accrued an incredible amount of power - equivalent to secretary of state, secretary of defense, and director of the CIA all rolled into one.
The man had personal connections all over the Middle East, and personal loyalty to him was often far more important than any loyalty to Iran.
Then, Soleimani was sent to Iraq in a very exposed manner, and even though the Iraqi prime minister says he was there to deescalate with the US the Islamic Republic has said no such thing.
This is because the Islamic Republic discovered he was planning a coup, and organised his killing with the United States.
The US helped because if Soleimani took over he would be far more popular than the current regime, and far more aggressive in the Middle East, forcing Trump to commit more troops there.
The Iranians needed the US to take him out due to the mass protests that were ongoing - if the regime had eliminated him it would’ve been the end.
This allowed them to use Soleimani as a martyr and symbol of the regime now, which has wiped out much of the dissent they were facing prior to his death
In order to appear strong, they had to retaliate.
That was these missile strikes, which were pre-arranged with the US to ensure the best outcome. (Note trump's comment about the early warning system working very well.)
Iran has now struck US bases, making themselves look strong, while the US can say there were no casualties and avoid having to commit more resources to the region.
Also see various peter zeihan videos on youtube for backstory.