1914 is still a magical year for WTS. Because they were expecting so much to happen that year, and because World War One started that year, it's proof that they were right all along. So they re-invented their doctrine afterward to say that they foretold that 1914 would be such an important year. They actually changed that to the year Jesus showed up invisibly, as they previously taught it was in 1874 or some such nonsense.
jwfacts that was linked by drwtsn32 is about the best way to understand it.
Putting any doctrinal reason behind, the best way to understand the change is that nobody really understood the 1995 change. It was explained and explained but it didn't satisfy anyone. "Open ended" generation? It could have been thousands of years. Without the end being moments away, this Jehovah's Witnesses cult doesn't have the drive it needs. They need to know that the end is near, very near, minutes away even.
By leaving the 1995 doctrine, there was no imminence. They didn't need to tie the generation to being "the anointed" but they needed to tie the generation to something just to show that there was an enddate. True, there's not much of an enddate yet, but there will be. Anyone who doesn't even do math very well can compute that there should soon be 144,000. Those that do math well know that it should have been reached before the second century but I digress.
I hope the WTS works up a new frenzy to get the numbers up by setting the enddate, at least setting up that it's very very very very imminent. That way, soon the "weak" JW's will tire of this game.