Unfortunately, people don't react that way in real life. Judas saw the miraculous healings Jesus did. So did the Jews. But they weren't converted. Also, it's very likely the soldiers took a dive before the angels and the light. Miracles, though, rarely convert. In the case of Paul, he was already religious (merely misdirected). Balaam was already a prophet, had seen an angel and yet fell. The soldiers most likely weren't Jews, and at the time Jesus was only sent to the lost sheep of the house of Israel. Add all this together and the soldiers most likely never saw a thing. In fact, who knows? They might have been executed.
But...on the other hand, how do you know they didn't join the church?
"There was an earthquake, sir! Lots of light. We lost consciousness right after we saw the angels."
"The what?"
"Angels. Two of them. Dressed in white. Very bright."
"You mean you engaged them in conversation?"
"No, sir. They glowed white. We needed sunglasses."
"Needed what?"
"Never mind."
"So there was an earthquake, angels that glowed and you feel asleep."
"Er...lost consciousness, sir."
"Whatever."
"Anyway, we've decided to serve God from now on!"
"Really?"
"Yes, sir. We've seen the light."
"That's nice. Kill them!"