Both Remington Arms - Union Metallic Cartridge Co., Inc. and Winchester Repeating Arms Co. greatly over expanded for war production for The Great War and then governments around the world pulled the plug with the Armistice, leaving them hanging. Remington Arms - Union Metallic Cartridge Co. incorporated in 1916, to raise capital for this expansion. They spun off a lot of their excess in 1920 and reorganized as the more streamlined Remington Arms Co., Inc., but still got into the cutlery business and other things.
Winchester also reorganized and came under new management, but the reorganization was fraught with injunctions and court fights, much brought on by a New Jersey lawyer, Elmer W. Demarest. Apparently, Arthur Young & Company's evaluations of WRA favored the majority stockholders at the detriment of the minority stockholders and there was a revision by Arthur Young & Co. Eventually Kidder Peabody became involved in financing and J.E. Otterson became president of WRA. This all eventually led to the amalgamation with Simmons Hardware, and Louis K. Liggett taking control, but delegating active management to others, mainly J. Clark Coit. It just goes from one horror story to the next.
In my mind the decline of Winchester began in 1902 when T.G. Bennett didn't take John M. Browning's deal on his autoloading shotgun and it was subsequently introduced in 1905 by the boys at Ilion. Winchester did have some 'golden years" as the hobby of the Olin brothers, but still never made a decent autoloading shotgun.