Source text: Nikita Bier, former product head at X, revealed that persistent safety threats against him and his family made it impossible to continue product development. While acknowledging the appeal of X's agile, flat organizational structure that allowed rapid pivoting toward critical issues like spam, Bier stated that individuals frequently appearing at his home with intent to harm created an untenable situation despite his willingness to accept visibility as a leadership trade-off. Bier stepped down from his role in August to transition into an advisory position, citing the need for rest after a period requiring around-the-clock commitment. During his tenure, X achieved record user growth and engagement, climbed 70 spots in App Store rankings year-over-year, rebuilt core features including the timeline, Android app, onboarding, notifications, and chat within 400 days, and launched nearly 30 new products. Benji Taylor, Singhai, and Dinkin Flicka have since assumed responsibility for design, core product engineering, and mobile engineering respectively. Target language code: de Translation instructions: This is the news article content. Please maintain the original meaning.