Be careful conflating agreeableness with empathy. In Big Five OCEAN, empathy is a sub-facet of agreeableness(A), but not the only one. Other sub-facets of agreeableness are conflict-avoidance, modesty, compliance, and naive trust in others.
Intuitively, it would seem to me those are more important contributor to success. In particular conflict-avoidance is a big contributor to being exploited by others. A person who scores moderately low on the aggregate agreableness(A) score could be both empathetic, but willing to stand up for themselves and make sure they're getting a fair deal.
Supporting this, the research has found that agreeable people do particularly bad in transactional, rather than transformative, leadership roles. When a team is working as a high-trust, high-cohesion unit, agreeableness is an asset. But when interacting and negotiating with third parties at arms length, it can be a major liability.