(spoiler alert) question about The Tainted Cup

Hi Redditors! First time poster, long time lurker.

Just finished Robert Jackson Bennet's Tainted Cup. On the whole, I quite enjoyed it. Well-paced, good world-building and really well written. Definitely more plot heavy than character driven but I think that's what I needed. I had two questions though, hoping other readers have answers.

1. !So were the deaths of the 10 engineers purely by accident because they happened to drink from the "tainted" cup?!<

2. !Were the 10 engineers also just meeting Kayagi Haza for patronage? One of the engineers said something about "engineers building the world and others just live in it", which makes it seem like they were out on some kind of vendetta or something, along with the Hazas.!<