because he had some level of intel to believe a major attack was imminent right after one of our embassies was attacked.
as others have pointed out and I haven't seen addressed, flip the script.
US embassy is attacked in Baghdad.
The next day Soleimani shows up in Baghdad with the guys behind the attack on the embassy. Trump knows, and orders a stand down.
Later on, lets say within a month, there is another attack on US assets/personnel.
would you be shrugging your shoulders and saying "oh well" can't blame Trump for not acting?
these are the type of decisions that age presidents decades over a four year period.