My theory is that the original plan was to wait until a few days before the election (probably the Friday before) to release the tape. This would ensure maximum media coverage with no time left for the Trump campaign to respond. When all of the Wikileaks revelations started hurting Hillary, they were forced to release the tape several weeks earlier in an attempt to counter all of the negative attention.
I agree. The dimoKKKRAT plan B was put into action earlier than they wanted because of WikiLeaks. That gave Trump time to shoot it down.