It is probably to do with the broken escalator, perhaps there was an accident there. But I can see the sense in it - it brings people into the station in the middle (between the two sets of departure boards, an underused space) and it avoids the conflicts as people "cross over" between the two sides which can when it's crowded be a bit unpleasant.
Which I would also see the sense in, had it been at all busy!
I would tend to agree that for those platforms it's more convenient to go up that way, and indeed avoids another set of escalators at the cost of doubling back up the ramp. However not everyone wants to do that walk! Plus anyone trying to come down from a train that way would have been directed up, around, and in through the front entrance.
I noticed the handrail seemed to have been lifted out so you may be right - perhaps there had been something occurring before, but it was long gone by the time I turned up!
The other two escalators were operational as normal, and people were still allowed to come down... Again, that particular escalator has been broken before [and indeed was only fixed the other day!] with no similar procedure.
It all seemed a bit overkill. Perhaps they had done it in preparation for the evening peak, but 2pm seems a bit keen!
Almost everyone exiting the Tube is going into the station anyway. There's not actually a lot else you'd take the Tube to around Euston that isn't nearer to another station unless you lived there.
There isn't a lot, but there also isn't no reason at all to exit the station, particularly if going somewhere close by but on the 'wrong' branch of the Northern line (I wonder how many people would rather walk a bit further in the direction of Warren St/Kings Cross instead of trying to change at Euston or Camden Town!)
I know I always get stuck behind people trying to walk down to Euston Road!
You also couldn't get to the lifts or the staircase up towards Melton/Drummond St as a result, which while not necessarily an accessibility issue is again an inconvenience for what I perceive to be little overall benefit at that time of day.
It's a real shame it wouldn't be simple to turn the 8-11 Tube access ramp the other way round or that could potentially work really well. Particularly if you bothered to tell people if their train was going to go from 8-11 so they wouldn't need to go up to the concourse at all.
Now that would be too good of an idea...
