The deterioration of the Rams is due to the ineffective management of their front office and team owner Georgia Frontiere's refusal to spend money for quality players, not John Robinson. The primary mistake the Ram front office has made is not using the Plan B free agent system as a means of strengthening the team.
The organization has rarely made significant trades, which is fine if a team drafts wisely, but the Rams have a recent history of wasted draft picks (Donald Evans, Mike Schad, Gaston Green, Bill Hawkins). While Robinson must take some of the blame, he can't control the fact that almost all of the Rams' recent picks have been signed too late to make an impact their first season.
Until the Rams decide to start spending money to acquire quality Plan B players and drafting wisely, the Rams will be a mediocre team at best.