Rumors are Soleimani may have been trying to out the Islamic Regime and working to make Iran more secular.
My opinion is that this is wishful thinking in hindsight, to support the " Khamenei requested the strike" rumor. I haven't read or seen anything to support this direction of thought, that he was shaping Iran to be more secular in any way.
3) America not only was working with Soleimani to combat ISIS, they were pretty much always aware of where he was.
IMO, more like a coincidence than a collaboration, as Iran wouldn't want ISIS doing ops in their borders. On the other hand, Iran funds militias which attack US forces and their allies..
Looking at the passenger rosters of any missing or shot down civilian airliner is always interesting. Page 1 of my Google search results and a few quick glances at recent news articles, and there's no public list of casualties(!).
Just my $0.02.