Beaming the two guys into their former selves was a "nice" way of avoiding KILLING them to get them out of the way. Maybe there was something that could be done with the transporter so that while they were beamed into their earlier selves, the "stuff" mAking up the slightly older versions sort of vaporized or melted away.
My big question has always been "How did the Enterprise passing thru those moments a second time cause the earlier version of the ship to vanish?"
I guess it was a "they merged" sort of thing. How or why, no explanation.
This from a show that allows for traveling backward in time in the first place, something that should be impossible. I think we can be a little forgiving. The laws of physics in the TOS universe must be different than they are here. There. Problem solved.
You want a REAL headache due to a time travel story? Try TAS's "Yesteryear".
Using the Guardian to view the past, in particular moments during which an adult Spock saved his younger self from death, caused the older Spock's presence in the past to be erased, thus cluing them into the fact he had to go back in time in the first place.
Huh?