Why is molybdenum that important in inorganic synthesis as well as biosynthesis of ammonia?
Why Molybdenum is Used in the Manufacture of Ammonia?
Molybdenum tubing has particularly good resistance to corrosion by
mineral acids, provided oxidizing agents are not present. It is also
resistant to many liquid metals and to most molten glasses. Molybdenum
is relatively inert in hydrogen, ammonia, and nitrogen up to about
1100 C, but a superficial nitride case may be formed in ammonia or
nitrogen.(Ref. 1)

Also, molybdenum has a special capability to form stable complexes with nitrogen atoms and hence molybdenum goes very well in biological reactions as well(See the link @user79161 has posted in the comment section). Recently, a group of scientists has developed a method for synthesis of ammonia using a dinitrogen-bridged dimolybdenum complex as catalyst and under very mild conditions of room temperature and at atmospheric pressure. However, the reaction mechanism of this new method is still unclear.

Reference

https://samaterials.podbean.com/e/why-molybdenum-is-used-in-the-manufacture-of-ammonia/
https://www.u-tokyo.ac.jp/focus/en/articles/a_00259.html (Picture)