"The temple that King Solomon built for the LORD was sixty cubits long, twenty wide and thirty high" (1 Kings 6:2).
The new temple was expected to be much larger and twice as high as Solomon's. Furthermore Cyrus was prepared to pay for it, yet it seems the resulting temple was smaller than Solomon's (3:12).
According to Josephus Herod blamed Cyrus for determining the measurements "… nor let any one condemn our fathers for their negligence or want of piety herein, for it was not their fault that the temple was no higher; for they were Cyrus, and Darius the son of Hystaspes, who determined the measures for its rebuilding; … they had not the opportunity to follow the original model of this pious edifice, nor could raise it to its ancient altitude" (Josephus 380-390).
The Bible does not apportion blame or explain why it wasn't built to specifications. Was the project was too overwhelming for the small group of newly returned exiles? Perhaps they lack the faith or willingness to commit to such an undertaking.
It is interesting that it was Herod, of dubious Jewish heritage, who restored the Temple to its original glory. Even Jesus' disciples were impressed: “Look, Teacher! What massive stones! What magnificent buildings!” (Mark 13:1).
God will fulfil his purposes. Let's exercise our faith and be part of that fulfilment, rather than leaving it to others.