Princess Kitana: To win your next match, use the element which brings life.
Johnny Cage: We got a guy with things comin' out of his hands, we got another guy who freezes stuff, and then there's a man, who as far as I can tell, is made out of electricity. I mean, how did he disappear like that? What is goin' on here? WHO is this GUY?
Sonya Blade: Let's just think this through. There is a rational explanation for all this.
Liu Kang: He's Rayden, god of lightning and protector of the realm of Earth.
Johnny Cage: Oh yeah. THERE'S your rational explanation.
Goro: Time to die.
Liu Kang: I guess you knew it would end this way.
Lord Rayden: Didn't have a clue.
Shang Tsung: Flawless victory.
Answer: Since the entire fight is focused on Liu Kang and Reptile, he could have possibly waited to see what the outcome of the fight was.