An Agreement of Desperation

Nelsen's aura stirred vigorously as he glared at Jacob with fury, but he was still sane enough not to attack Jacob when they were in the champion space. 

Furthermore, attacking Jacob would only make things worse for himself because he couldn't see through his power level the moment he laid his eyes on Jacob, even with his unique visual ability. 

That's why he wanted to provoke him into attacking, as SAAI would instantly react, and he could get rid of him. 

However, the tables have turned, and he never saw it coming. It could've been fine if he was alone, but all this happened in front of his enemy, which revealed his weakness, and now Jacob can easily take full advantage of it. He knew because he would. 

Now, he even regrets clearing this trial condition. Not only did he double-cross the King of Dead, he ended up exposing himself to an enemy like Jacob. Moreover, when Lucy and his other enemies discover this, they will not let him go either.