I heard this explanation the other day as to why this happens,
Imagine I had a special deal with the bank to earn 20% interest on a certain bank account, in the bank account was $1000 earning 20%, So the bank account had a net asset backing of $1000. If I were to sell this bank account how much should it sell for? Some people would be happy to pay $2000 or double it's NTA backing because of the high return would still earn 10% based on their investment of $2000 so this asset will trade well over nta.
However,
If this same account only earned 5%, the average person would still want to earn 10% on their investment so would only be prepared to pay $500 dollars for the $1000 of NTA backing.
It all comes back to the percieved future return on equity and property has a low return on equity.