It's pretty clear from the Manning trade that in the "final days" Chiarelli was simply trolling the team... seeing what he could get away with and the Koskinen trade was just another wild one that got through. Maybe he was pissed that he was essentially pushed towards the Reinhart deal without wanting to do it and that made everyone around the league think... "what a goofy GM Chiarelli is"... and in the end days he just said f*** it... here's some more garbage as my rep is screwed league-wide anyway.
Chiarelli acted like a typical GM in a death spiral. He made poor trades with impaired judgement that the end was near in his Oilers tenure. The dead man walking GM playbook is pretty consistent.
- Panic move 1: fire the coach.
- Panic move 2 when that inevitably fails: start trading for perceived immediate help - either roster players or with prospects.
- Panic move 3: his keys to the building are changed and GM is invited to watch future NHL games from his tv at home.
Chiarelli was a hands-on GM who insisted upon the executive title as well following being pushed out the door in Boston. He insisted upon the autonomy to run the team as he saw fit. He made the Reinhart trade trying to fast track this franchise's development after falling into the golden goose of drafting Connor McDavid. Chiarelli's on record about discussing the deal with Snow for a month or so leading up to the draft. Had live AHL viewings of Reinhart and Memorial Cup as well. This was Chiarelli's deal without doubt some positive support and influence by Oiler management types who had seen the player going back to bantam scouting days. Chiarelli pulled the trigger and blew it.
After his panic trade moves, he incredibly still had autonomy to sign Koskinen to a big money, multi-year deal with no trade provisions as the fairly dust on a sole contractor negotiation.
Unlike your scenario, amazingly enough, one of the NHL's better GM's thought enough of Chiarelli to bring him into the St. Louis organization that was on its way to being a Cup contender. So it appears Chiarelli maintained a reasoned reputation among his NHL peers despite the classic failing GM playbook he executed which by his last days left this team expensive, shitty, and with no NHL roster depth.