The Raiders franchise is a dumpster fire. They don't often get included as on the same level as franchises like the Browns and Jets, but they very much are. They've only had 2 seasons in the last 20 with a record of over .500. They haven't won a single playoff game since 2002, and they've only even made the playoffs twice in that same time frame. After over 2 decades of sucking they still have very little to show for it. They have one of the worst rosters in the league. Bowers and Crosby are pretty much their only pro bowl level players.
Pete may be complicit in some of the decisions they made last off season, like spending a very high pick on a RB when they had far more pressing needs, but these are the types of things the Raiders have been doing for decades regardless of who their coach is.
I agree that Pete should probably move on from trying to coach at the NFL level, but I also don't think he ever had much of a chance for success in LV with that horrible, dysfunctional, incompetent mess of a franchise.