WHY DID WINDOWS 95 SETUP USE THREE OPERATING SYSTEMS?

Summary from the TLDR Web Dev newsletter

Windows 95's setup process utilized three operating systems (MS-DOS, Windows 3.1, and Windows 95) to handle upgrades from various starting points. Instead of creating three separate setup programs, developers cleverly designed a chained system using an MS-DOS program to install a minimal Windows 3.1 version, followed by a 16-bit Windows program for core setup tasks, and finally a 32-bit Windows 95 program for final configurations, which minimized code duplication.