Here's why, in rough chronological order: - Mid to late 1970's - people discovered they could build microcomputers, cheaper and less capable than the minis or

Here's why, in rough chronological order: - Mid to late 1970's - people discovered they could build microcomputers, cheaper and less capable than the minis or mainframes of the day. - Visicalc showed that micros could be a good business tool without all the expense of huge shared mini or mainframe systems. - In 1981, IBM made a micro, so people started taking it seriously. Microsoft made a really good business decision to license not sell MS-DOS to IBM. It was the cheapest OS so the one most people picked. - Rest of the 80s: Clone manufacturers made the hardware cheaper and cheaper. Clones also ensured Microsoft's OS worked as most software depended on it. This was the beginning of the downfall of IBM. Microsoft continued to acquire/produce business software for MS-DOS. - PCs gained capability over the years. Microsoft introduced Windows 3.x, and people really liked it despite it's numerous flaws. With various GUI programs starting to become common and easy to do on the hardware, business interest of this platform flourished and it with Microsoft and Adobe products became the default. - 90's: Microsoft started using OEM agreements and other business tactics to ensure OSes other than Windows were difficult to purchase. The Internet craze started and the PC was its primary thing that brought that to consumers in the 90's. After Intel came out with the Pentium, the Wintel marriage was solidified and thus began the downfall of CPUs in PCs other than x86. - Microsoft continued to ride this domination wave until Javascript provided a way to deliver a desktop like experience without having to go througH Microsoft at all. 9/11 slowed things down everywhere. Microsoft let IE6 rot while it was working on Vista, giving Mozilla (backed by Google) a chance to sneak in a way to deliver a non-Microsoft experience on whatever platform was running the browser. - 2007 - the iPhone - that began the shift from PCs to mobile for everyone. Because people wanted the Internet in the 90's, and email, and chat, and all it's good stuff, but they didn't really care about Windows. Windows was just what worked at the time. Apple adopted the walled garden model - meaning the browser was still the only way to deliver an experience outside of permission or control of another company. Why wasn't Microsoft in this position? It thought it was (and it looked lke it was)... it thought it could sit on its ass, collect OS license money and boss around both OEMs and cellular carriers like PC OEMs. What Apple did in the 00's with iPod->video iPod->iPhone iteration and timing is either super shrewd or super lucky. - 2014 - cloud services - everyone finally saw what Google was doing and copied it, which was just a copy of the pre-micro mainframe way of doing things, but with prettier terminals that are virtualized and can do graphics and audio now. Unfortunately businesses don't want to give up Excel.