Marketing is a big portion of it. There’s also less obvious versions. Microsoft was busy making deals behind the scenes with OEMs for a long while with the intention of getting Windows to be the default OS in stores. Early OEMs didn’t just wake up and start building for Windows. Bill Gates showed up at there office and convinced them to.
Apple donated a bunch of computers to schools. Many people just believed that it was because they cared about education but really it is an attempt to get kids hooked into the Apple ecosystem early.
Building brand loyalty isn’t just about advertising and it’s not even about making the best product. Early and repetitive access is more important. Advertising and product placement are more about awareness than loyalty. Loyalty is generally exploiting people’s fear of change.