If the emperor showed up claiming to be my daddy and forced me to abandon my slave-gladiator-rebel allies on the eve of battle with the noble armies coming to crush them, I too would be a terrible manager and betray him at the first opportunity.
Anyway Angron was set up, he didn't choose to get the nuralink installed
The Emperor could have probably had him onside forever if he'd just teleported down and killed the slavers but no he was too busy arguing with Malcador that there should be no girlz allowed in the army because they have cooties.