Due to the genocide Diluc committed to the Nation of Snezhnaya 3 years ago to avenge the death of his Father,"Crepus"...that's have been killed by an ordered group of Fatui Skirmisher of the Fatui Harbingers and now...Diluc might suffer the same tragic fate as his Father,

“from The Divine order of Punishment of the Archon of Snezhnaya”

A group of Fatui Skirmishers were dispatched over to capture Diluc and because he was in a weakened state,The Fatui managed to capture him.