They could've waited and he would've shut down the system and they could've crossed through.

But no, now they had an even bigger problem, and Jim--

All Jim could do was act. He reached out to grab both Kryptonians, and shut a tight shield around all three of them - though mostly around them. "Wrecking ball," he muttered, knowing that they could hear him even if nobody else could.

With the shield from his arm, they could push through the armed horde like bowling through pins. Just... harder.