To say the idiom cannot see the forest for the trees means that a person or organization cannot see the big picture because the focus is too much on the details. It would be like someone needing to paint an entire house in one day, but spending half the day on picking out the right color.
A related phrase is the proverbial tree falling in the forest. Proverbial means related to an idiom. The tree this is speaking of is the philosophical question: if a tree falls with no one to hear it does it still make a sound? The idea is that a sound is heard so if there is no one to hear it, does the sound still exist?
Occasionally the phrase proverbial tree will refer to the first idiom, or to another phrase involving a tree. For clear meaning it is best to use the full phrase falling in the forest.
Abe criticizes the opposition camp for not seeing the forest for the trees in its attempt to highlight the dangers for SDF members. [The Japan Times]
I’m not sure I even want to be a smart man if it means getting so focused on the trees that I can’t see the forest. [Wealth Daily]
The answer is not that difficult if one would stop looking at the proverbial tree, but stand away and look at the forest instead. [The Hill]
The Qatar-owned cable news network is, though, the proverbial tree in a forest that implodes with no one around to hear. [Breitbart News]