Short answers, pulled from the story.
Steve Jobs acquired NeXTSTEP in 1997 for $429 million to save Apple from bankruptcy. This purchase brought Jobs back to Apple and provided the Unix-based architecture that became the foundation of macOS.
Mac OS X 10.0 launched on the 24th of March 2001 and was criticized for being slow and lacking basic features like DVD playback. Critics described the early release as dog-slow and feature-poor, though it introduced revolutionary concepts like pre-emptive multitasking.
Apple announced the transition from PowerPC to Intel processors on the 6th of June 2005 at the Worldwide Developers Conference. The first Intel-based Macs were released on the 10th of January 2006, and the transition was completed with the release of Mac OS X 10.6 Snow Leopard in 2009.
OS X Yosemite released on the 16th of October 2014 replaced the glossy Aqua interface with a flat, minimalist design inspired by iOS 7. This shift represented a fundamental change in how Apple viewed the relationship between its desktop and mobile operating systems.
Apple announced its return to in-house processor design with the M1 chip on the 22nd of June 2020. The first macOS version to support Apple Silicon was macOS Big Sur, released on the 12th of November 2020.
In 2021, Apple fixed a critical privilege escalation vulnerability in macOS Big Sur but left macOS Catalina unpatched for 234 days, allowing the vulnerability to be exploited. Apple responded by introducing features like Lockdown Mode and Rapid Security Response updates to protect users from sophisticated threats.