Having a bit of faith in the doctors involved, it was probably a secondary infection

It’s quite a common process known as a superinfection or secondary infection. Typically a bacterial infection occurs on top of a viral one. The mechanism in something like a cold is that the virus causes congestion, increased mucus secretions, and just generally a bunch of gunk which doesn’t get cleared very well. That acts as a nice breeding ground for bacteria which can now gain a foothold.

Typically that bacteria is just from your own skin and is normally harmless when kept in check by the other skin bacteria around it, but it gets a new advantage from the previous viral illness and grows unchecked.

We add an extra medicine to block an enzyme that would convert the medication we want to be converted in the brain too early, out in the peripheries.

You mean no benefit to longer hours. That’s how the study should be interpreted

Mostly right. The more technical explanation is that blood is squeezed from the arterial space into the venous space. Veins return blood to the heart -> therefore increased preload

Most of your total vasculature is in the peripheries / not in the great vessels.

Widespread vasoconstriction therefore preferentially forces blood away from the peripheries and towards the heart.

This results in increased preload.