RF brake locked up. Why?

That's messed up.
the strut and it's associated spring are missing
the shoes appear to both be the same length
the adjuster seems to have way more thread visible than should be

without the strut, there is no way for the self-adjuster to work; and the disco'd cable ensures it.EDIT;see below
In your case now, if the shoes stayed out, it's all about the fluid not returning to the master, And there are just a few ways for that to happen. In order of likelyhood;
1) non-functioning Compensating port (easiest to check)
2) faulty wc, or shoes not returning to the anchor pin.
3) faulty flex hose
4) debris in the system
5) faulty distribution valve

BTW; the adjusters are usually marked L, and R; if you put them on the wrong side,IDK I've never done it, but it seems to me that they would adjust when moving forward, instead of only in reverse. Also, the cable goes on the trailing shoe

Silicon fluid is fine, leave it in there, it has nothing to do with your problem. I'm with 66fs, install it and forget it, and forget what the naysayers propone; mine's been in there for going on 20 years, and in the KH 4 piston calipers, which were known they say, to be troublesome. bs.

Edit: this is wrong, the strut is for the parking brake, and does not need to be there.