OEMs figured out that they could build a custom recovery image with the bloatware included (including on Windows 8). Windows 10 supposedly lets you delete the package that includes the bloatware, but I haven't tried it.
Windows 8 and 10 also have a lovely feature called the Windows Platform Binary Table. This allows OEMs to write an application into the UEFI, and Windows will automatically deploy to memory and run it with admin privileges each time it boots. The intended use was for installing drivers and anti-theft agents, but of course it was immediately used to drop bloatware/malware. This vector works even on entirely fresh installs, and there is no mitigation except obtaining a clean, signed UEFI image.
http://www.howtogeek.com/174587/refreshing-your-pc-wont-help...
http://www.howtogeek.com/216751/bloatware-banished-windows-1...
Windows 8 and 10 also have a lovely feature called the Windows Platform Binary Table. This allows OEMs to write an application into the UEFI, and Windows will automatically deploy to memory and run it with admin privileges each time it boots. The intended use was for installing drivers and anti-theft agents, but of course it was immediately used to drop bloatware/malware. This vector works even on entirely fresh installs, and there is no mitigation except obtaining a clean, signed UEFI image.
https://www.techdirt.com/articles/20150812/11395231925/lenov...
http://www.howtogeek.com/226308/the-windows-platform-binary-...