This installer is primarily legacy support. It downloads older libraries (DirectX 9.0c, 10, and 11) that older games might still require. Modern DX12 games rely on the OS, but older titles (like Fallout 3 , classic GTA , or MMOs from the 2000s ) will crash without these specific legacy files.
for older DirectX components (if an old game complains about missing d3dx9_xx.dll , etc.): directx 12 downloads
This implies a corruption in your Windows System files, as this file is native to Windows 10/11. This installer is primarily legacy support