What is the fine-grained topic of the following text: With the rest of the management team remaining in place led by interim CEO and executive chairman Taeyong Lee, it’s possible Felesky fell on his sword for Horizons’ mediocre performance in recent months at a time when Vanguard has been feverishly gathering assets. Only return the topic.
Changes in Horizons' management team amidst company's mediocre performance.