I find it hard to blame the clubs. The issue here is the IRB imo. The only solution to avoiding this kind of issue in the future (as well as other kinds of injuries) is through limiting the number of games that a player can appear in over a season. Clubs will not voluntarily take this step, because they lose their competitive edge. It will cost a team points over a season, to give players the kind of rest that they need. This is particularly a problem for internationals, who have the added rigour of the international game, plus being (normally) the first name on the team sheet for clubs - and these are exactly the types of players that clubs do not want to rest, where they can help it. It is a race to the bottom, where the teams that try to take the moral high ground find themselves behind the teams that flog their players, because they go for extra games without their stars.
Therefore, action has to be enforced, and the IRB is the only body that can cover all bases.