Full sentence is too long for the title of a post:
'Она улетела, а тоска осталась необъяснённой, ибо не могла же её объяснить мелькнувшая как молния и тут же погасшая какая то короткая другая мысль: ' (Bulgakov again)

My poor attempt at translation yeilds this:
It flew off, but the gloom remained inexplicable, since it could not explain another 'flashing like lightning and then dying away' brief thought:

The 'proper' translation seems to be:
'It flew off, and the anguish remained unexplained, for it could not well be explained by another brief thought that flashed like lightning and at once went out;-'

But for this to be correct, I think объяснить would need to mean 'to be explained by' not 'to explain.'

I know my transalation is wrong as 'мелькнувшая как молния и тут же погасшая какая то короткая другая мысль' is nominative, not accusative case.

Does 'объяснить' mean 'to be explained by' here, if so, why? Or is it something else.

Thanks.