[manephelien]

One reason why there was a problem was that the Jedi had to choose between serving the universe and having a family. This meant that a lot of disenchanted Jedi were thrown out of the Order or left voluntarily, prime candidates for a Sith lord to recruit a new apprentice from. This meant that even if there were only two Sith, they had candidates waiting in the wings and minions to do their bidding who had some training in Force use without being fully Sith.

So my take on it is that the Jedi contributed to the imbalance in the Force by concentrating too much on the universal and ignoring the personal completely, leading to lots of disenchanted Jedi. Enforcing Senatorial rules and indirectly serving the Sith Lord certainly contributed to this imbalance, even if most Jedi appeared unaware of Palpatine's evil until he changed, by which time it was too late.

While Anakin was the Chosen One, he would never have seen the error of his ways without Luke. Vader destroyed the Sith order by killing his master even if it meant his own death. Luke made sure the errors of the old Jedi Order could never be repeated by allowing them a personal life.