Me too. I think it just happened that way. I know the band didn't go into recording OBC saying "Okay, we'll make give this a concept and then follow that same pattern for our next album." I just think the conceptual *layout* of OBC wound up having an influence on the blueprint of DSOTM, i.e. the music following a concept of losing your state of mind through a series of different events or elements. Which leads me to Steechy's comment, I may have been too abstract earlier and didn't elaborate well enough. If you don't get what I'm saying or at least still think I'm crazy, I'll give up on you:

Okay, check this out: Pink Floyd, as quoted from an interview, turned the OBC soundtrack album into a concept thing that had a story to it based on the film, which was: ordinary person goes through series of events that changes their state of mind/persona. AND, Floyd put the things in a sort of SEQUENCE or order to articulate that.
Alright...
DSOTM was about how the pressures of society can lead to MADNESS, and again, Floyd put them in an order that showed those things leading up to insanity on 'Brain Damage.'
So...
Both albums wound up with a concept about how certain elements/events/surroundings can change a person's persona to where there's "no going back" (or to where the sun is eclipsed by the moon). AND, both albums showed each of these things things *leading up* to a loss of a civilized persona or loss of sanity.
Therefore...
I think that by the time the planning for DSOTM came about, Floyd said "Okay we're making this concept album about madness...yes, Roger it was your idea, we know...anyway, we're making this album about madness. So, how should we express it? Maybe we should do what we did with OBC, but instead of describing a dangerous adventure leading to a change in mind, let's put work, travel, time, death, money, and violence ALL LEADING UP TO insanity."

Sorry if your thought is still
"Okay, you must be on crack
Alright...
I don't know where you pulled this theory out of
So...
You are still crazy."