All of the above combined with the fact that it has just led to some truly terrible football.
The international version of the sport is always 5-10 years, tactically, behind the club game, but the week or so most of the big teams have had to truly prepare compared to the usual 3, has ensured almost every team is playing in the same basic style and that the best players are, if not injured, then just exhausted from the hectic season.