King Elbas had managed to defeat the attacks of two powerhouses and save Ravaging Demon at the same time. The latter eventually regained his foothold and resumed his flight toward the leader of the Royals.
Great Elder Diana couldn't interfere with him. She could use abilities that didn't rely on her precision, but their power would be lower than her main attacks. King Elbas would fend them off with some casual spell.
She was even on the other side of the battlefield, so she didn't have time to fly through the chaotic area and intercept Ravaging Demon before he reached King Elbas.
On the other hand, Chasing Demon was near the Patriarch of the Elbas family and could see Ravaging Demon rising in the sky toward his ally. His titan was no more though, so he lacked offensive methods at the moment.
Both Great Elder Diana and Chasing Demon had yet to attack King Elbas directly. They had avoided bringing their battle on that stage to maintain the focus on Ravaging Demon.