Complex sentence: Yet, so long as state commercial and cooperative institutions were incapable of meeting the demand for goods and services, NEPmen were tolerated, however many former NEPmen ultimately fell victim to the repression of the Great Purges.
Split into simpler sentences: Yet, so long as state commercial and cooperative institutions were incapable of meeting the demand for goods and services, NEPmen were tolerated. Many former NEPmen ultimately fell victim to the repression of the Great Purges.