Back then Apple had made waves introducing Safari, which was not only great and cross-platform, but had an open-source renderer (WebKit), and JavaScript engine (JSC). Safari was crushing web standards while IE lagged, seemingly trying to purposefully choke the web to stop it from canibalizing Windows software. Apple was betting on web: one of the big features on their brand-new Mac OS 10.4 Tiger was the Dashboard with widgets that were all built with HTML/CSS/JS, and they were shipping a new, free IDE (Dashcode) to build them too.
Mac OS X was heavily marketed for being UNIX vs Microsoft's proprietary and closed Windows NT. They were building Safari and iTunes for Windows, and had just introduced the first Intel Macs; it seemed like they were out to put a fight against a very closed, very walled, and very incompatible Microsoft who had gotten too comfortable with the Wintel and IE monopolies.
Fast-forward two decades, and not only can you now run a native GNU/Linux environment on Windows, but the best IDE out there is web-based and open-source Microsoft software while Apple lags behind on developer experience. They seems to have missed the bus on web technologies too. They went from leading charge with a stellar browser pushing web standards forward, to being an obstacle out of fear Safari might canibalize iOS software.
Apple hasn't gone full early-2000s Microsoft (thankfully) and Microsoft hasn't gone full early-2000s Apple (unfortunately) but times have really changed.