1) Injuries to 3 starters on the offensive line, and then also to 1 of the guys that came into replace them. That spells doom for any team built around the run game. This is what set the train in motion to derail.
2) The inability to adapt in order to survive point #1. This was/is owing in large part to having worst QB in the league. Once we no longer had an offensive line that was close to NFL calibre, the run game could no longer be the focus. The solution? Stop leaning so heavily on the run game. Start throwing the football. Preferably with quick, short-to intermediate throws that don't ask too much of your sub-par offensive line in pass protection. You know.... like all the others teams with bad o-lines do. Sadly, for the Rams, this was not a feasible solution with Foles unable to hit wide open receivers even when he has a clean pocket.
3) Poor offensive play calling and strategy due to a bad OC. This caused an inability to adapt to #1 and #2 -> once the run game was gone and the obvious solution of short, quick throws was also off the table, we were cooked. Cigs was in way over his head and had no idea what to do next at that point. He was lost. So we got to see Gurley run straight into the teeth of the defence all Sunday. Or the run game abandoned entirely with shots downfield that resembled blind prayers, hoping we could get lucky with a big play, rather than planned and strategic play calls. To be fair, most (all?) OCs would have been screwed in light of #1 and #2. But Cigs took it to another level. He had a total inability to be creative and even come up with 1 possible solution. Perhaps unsurprisingly. It would have taken a genius to figure out how to turn the Rams lemons into lemonade. We had a guy with ZERO experience as an NFL OC prior to the 2015 season.
4) No confidence. Sports is in large part mental. It is crazy how once players are "feeling it" they look 10x better, even though their talent level is obviously unchanged. After so many poor displays, confidence will not be huge. That's not to say the team will be demoralized or negative. But the football won't seem to "bounce your way" in a losing streak as it does in a winning streak.