If Chelsea didn't sell all of these players who weren't serious, changing coaches wouldn't have any impact on the team's success. In fact, nothing would change even if they kept switching coaches for the next two years.
Chelsea have tried different coaches but their is no changes in Chelsea's performance, their performance keeps on getting worst after changing their coach, so buy now we should know that coach is not only the problem Chelsea is having, am not saying that Chelsea those not need a experienced coach, but Chelsea also need players that are dedicated to work for the team, not players that are just receiving money and they are not putting any effort to move the club forward. Chelsea have to flush out most of their player's, most of them are not really ready to work for the club.