Last year there were a couple national articles on the growing number of strikeouts across baseball. This year, with the crazy K pace, there has been more media attention and speculation as to why. This was discussed briefly last month in this forum.
Anyway, after thoughts of the the scouting being better or the pitchers being more specialized and the pitching being deeper and even the drop in PED using being the answer, the primary cause may simply be the rule changes to 8.01 in 2007 and the interpretation changes of 2012.
Hitters, pitchers and coaches seem to be slowly coming to the same conclusions. Pitchers not having to keep their ENTIRE pivot foot in contact with/ in front of the rubber gives pitchers 44+ inches of angle from 1st to 3rd base to deliver from, instead of just 24 and creates a new and almost unfair advantage. Pitchers can also now have their pivot foot lose all contact with the rubber while in the full windup if it reengages before release. Pitchers have recently been using this to land their foot at a drastically different place on the rubber to shift the hitter's view last moment and to release far from where they began the windup. This was not intended in the rule change. It was so pitchers would be ok if their back foot slightly lost contact as the foot shifted to its side, which was common. Pitchers are using the new freedom to as much advantage as possible!
It all may be as simple as the supposedly subtle rule changes and pitchers getting used to them and learning how to get away with more.