The phrase 'main impetus behind' is correct and usable in written English.
You can use it when referring to the primary driving force or cause of something. For example, "The main impetus behind the research project was to find a way to reduce air pollution."
Ligand-targeted nanoparticles have been the main impetus behind the progress of nanomedicines towards the clinic.
The main impetus behind America's tilt back to Europe is economic — something of a paradox given that Europe's economy is in the doldrums.
The main impetus behind the law is religious violence – an ongoing problem in India that can be inflamed by hate-filled postings.
But the main impetus behind the prince's remarks may well have come from another source, one Americans are intimately familiar with: poll-driven domestic politics.
And third, Zarqawi's death seems to have removed the main impetus behind exporting Iraq's violence.Zarqawi's decision to bomb three hotels in Amman in November 2005 backfired badly, causing a wave of revulsion, especially in his native Jordan.
Each adding significant collections to the Division's holdings: Simons led expeditions to Wyoming, the Siwaliks of India and Pakistan and the Fayum of Egypt, while Ostrom's research and writings on the functional morphology of dinosaurs and the evolution of birds served as the main impetus behind the "dinosaur renaissance" at the end of the 20th century.
The principal impetus behind collecting and artistic patronage throughout the later Middle Ages was religion.
SRI conceived the study, participated in its design and coordination, and was the primary impetus behind the pedigree development.
The main impetus for the industry to leave lead behind is a ban on lead in electronics imposed by the European Union.
But in design, the main impetus came from Europe.
Growth is the main impetus for globalization, though.
