I had uninstalled and reinstalled D4 and still this problem.
This may be from my DCS World simulator.
because in my settings I have to check a box ‘VR’ and when I run it, it opens steam VR and simulation.
So I unchecked this box when I do not want to use the VR headset, because I want to create a mission for example.
And so steamVR and D4 do not launch.