Schweitzer's Famous Quote - Removed?

Scot McKnight in his short survey on the historical Jesus notes this famous quote by Albert Schweitzer.

“There is silence all around. The Baptist appears, and cries: “Repent, for the Kingdom of Heaven is at hand.” Soon after that comes Jesus, and in the knowledge that He is the coming Son of Man lays hold of the wheel of the world to set it moving on that last revolution which to bring all ordinary history to a close. It refuses to turn, and He throws Himself upon it. Then it does turn; and crushes Him. Instead of bringing in the eschatological conditions, He has destroyed them. The wheel rolls onward, and the mangled body of the one immeasurably great Man, who was strong enough to think of Himself as the spiritual ruler of mankind and to bend history to His purpose, is hanging upon it still. That is His victory and His reign.”

[Albert Schweitzer, The Quest of the Historical Jesus, pg.370-371.]

If you follow the link in the reference, and scroll down to page 370-1, you'll see the quote in that edition. McKnight claims that the quote was removed from later editions of his work. My question is simply this: WHY? Did Schweitzer change his mind? Did later editors remove it, is there any explanation for this phenomenon, or is it just an enigma?