a 5 month pre-season period is very rare in professional football or even rugby union, however from the information you have given it looks like their strength programme was poor.
A lot of S & C coaches in football, at least in the UK come from an exercise physiology background and as such are more like ‘scientists’ rather than coaches. As a result of this their knowledge and application of strength training is often very poor, this coupled with the mentality of football players not needing to be strong often leads to an endurance based programme with little or no regard given to strength development.
Also though you can improve power without the use of Olympic lifts, but by using jumps, medball throws and barbell exercises with sub-maximal loads. I like using Olympic lifting but this is not to say power can only be achieved through this training method.