What causes Kerbals to become brain dead debris?

Jebediah was testing out my new monopropellant lander on the mun. After landing it was obvious that he was some 300 units short of making it back to Kerbin.

I designed and sent a lightweight refueling lander with grapple arms to fill Jeb's lander back up. It was hex-radially designed with interspacing command chairs/monopropellant tanks with grapple arms around a 1/4 orange tank with a poodle engine. These radial command chairs were piloted by brave & stupid white suits who were chosen for their ability to have unlimited suit lights.
Now unfortunately I ran short of fuel while coming into the target area and did a very hard landing.
Luckily the refueler only suffered damage to the poodle engine and 2 of the grapple arms while retaining it's solar panels and SRS. So I decided to roll my way on over to Jeb.
While I was rolling I would lose a Kerbal every once in a while as they fell out of their command chairs. No problem I thought I can just walk em back in.

However, after switching to them they wouldn't move they just stand there and when I mouse over them it breifly says debris!

Normally when I kill a Kerbal they go poof and are normally travelling at a much higher velocity.

Do command chairs cause Kerbals to become debris? If so how does this happen? (like is it from hitting the ground or just being jostled around in a giant wheel, etc.) Would a roll cage prevent this?

Pic of recreation on launch pad Poor Jeb is debris...