Kaizen fully trusted Arthas to stop Thenomor or at least slow him down. He rushed up the steps to get to Niah as fast as he could, but since the former queen was surrounded by New Royal Guard soldiers, most of those who were too close to her could not run in time from the expansion of the reddish bubble.
That being the case, there was a wall of soldiers that were being controlled by the former queen in his way.
Kaizen knew that he didn't necessarily have to get as close to Niah as a normal person would need to get the necklace. Just a few feet would be enough to reach with <Telekinesis>.
When Kaizen got close enough to the queen, he dropped the Eye of Storm on the ground and prepared to snatch the necklace from her using his right hand. Suddenly, he felt a tightness in his throat as he used <Telekinesis>, and those uncertain-looking black tentacles coming out of her necklace began to react even more violently.