Why did Director Krennic personally go to the data vaults?

Question

During the Battle of Scarif, Jyn and Cassian are in the data vaults and dozens of Stormtroopers are killed trying to make their way in to stop them. Then Director Krennic decides to personally go down there to stop them. I can't understand why he did this personally given that:

• He seems to be in charge in the war room and thus by leaving is neglecting important duties as a leader
• He is not nearly as well armed, armored, or trained as the dozens of Stormtroopers who just died trying to get in

So why did he personally go down to the data vaults?

Answer 1

There were two reasons, covered in Freed's official novelization (Chapter 20):

1. He saw this as personal. He was focused on Galen already. And he realized Galen's daughter was against him now.

   KRENNIC TRIED TO FOCUS ON Galen Erso’s communications archive. ...
   Galen had set this in motion. If he had reached out to allies in the Rebellion, sent the traitorous pilot to contact those allies on Jedha, summoned those allies to Eadu, arranged for them to hound Krennic even after Galen was rotting in a mudhole of a mass grave…
   Krennic stopped short. He remembered now, on the Eadu platform—a flash of dark hair and a face covered in ashes. He recalled the voice saying: You’ll never win. But it was Lyra who spoke, not Galen.
   “—unauthorized access at the data vault.”

   Krennic shut out the man’s nattering. The rebels were inside the Citadel. They were inside the vault. They were determined to steal the schematics, to find an imaginary weakness, no matter how many lives they lost. They were determined to haunt him on Galen’s behalf.

2. He saw General Ramda as unable to deal with the problem, and there were too many unlikely wins for Rebellion already, so he adopted "If you want it done right, do it yourself" stance.

   And Ramda wasn’t up to the task. The shield gate was shut and escape was surely impossible; yet too many impossibilities had already occurred for one day.
   He hurled his words behind him as he marched toward the stairs. “Send my guard squadron to the battle! Two men with me!” There was someone in his way; he roughly shoved the body to one side, not bothering to identify the man’s face. “And get that beach under control!”

   (and earlier, his opinion of Ramda:)

   General Ramda was a fool, and Krennic had already decided to have him tried and imprisoned for gross incompetence.

Answer 2

Krennic's fatal flaw is that he believes himself to be a man of action, an equal to luminaries such as Tarkin. When something goes horribly wrong, he seeks to put himself at the centre of the action, believing that his personal involvement will somehow rectify the situation.

Like many (most?) middle-management technocrats who think themselves worthy of the top job, he lacks the ability to effectively delegate in a crisis when any fool could have spotted that the attack on the beach was a diversion.

“Send my guard squadron to the battle!” The death troopers would help break the back of the rebel assault, but Krennic had to hit the heart of the problem himself. “Two men with me! Get that beach under control!”

Krennic shoved his way out of the room, leaving others to worry about the rest of the battle. If he wanted whatever was going on in the data vault stopped, he would have to put an end to it himself.

_{^{Rogue One: A Star Wars Story – A Junior Novel}}

Tarkin, by comparison sees to the heart of the problem within seconds and takes ruthlessly decisive action.