“And they brought the Mishkan [Tabernacle] to Moses.” [Exodus 39:33]
“They brought the Mishkan to Moses” – because they were unable to assemble it. Since Moses had done no work on the Mishkan, G-d left its assembly to him. [Therefore] no one had the power to assemble it [except Moses].” [Rashi]
Moses was distressed at the fact that he did not participate with them in the work on the Mishkan… G-d said to Moses, “Since you were distressed that you had… no portion in the work on the Mishkan, those wise men were unable to assemble it [and the assembly was left to you].” [Midrash]
How could Moses feel that he had “no portion” in the Mishkan? He oversaw the entire project! All of the detailed instructions for the Mishkan were communicated by G-d through Moses.
Moses missed the chance for hands-on, physical involvement in the work. Despite the critical role he played, he yearned for the opportunity to participate in the actual labor alongside the other Jewish artisans.
Moses’ legendary accomplishments were unique in history: leading the Jews out of Egypt, splitting the Sea, bringing the Torah down from Sinai. Moses’ role in the Mishkan, too, was irreplaceable. But Moses felt he was missing something because he lacked the opportunity for hands-on involvement. When one truly appreciates the value of a Mitzvah, there is no such thing as “enough.” Every spiritual opportunity is priceless and irreplaceable. G-d had to intervene miraculously, making it impossible for anyone but Moses to erect the Mishkan, in order to satisfy Moses insatiable craving for spirituality.