Welcome to the silent agony of the online web installer.
Once you have that file on a USB stick or a secondary hard drive, you are a digital sovereign. You can reformat your PC ten times. You can take your rig to a cabin in the woods with no Wi-Fi. You can install Windows 10 on a nuclear submarine 3,000 meters under the sea. It doesn't matter. Double-click the .exe. Twenty seconds later, DirectX 12 is home. download directx 12 offline installer
This is why the is the unsung hero of PC gaming. Welcome to the silent agony of the online web installer