Why do some individuals who are productive PhD students at leading Western institutions, then publish infrequently as faculty in their home country? I am a computer science student from Turkey. While I was checking the websites and publications of various CS Professors in Turkey for my future studies, I noticed a strange trend. (Excluding minor exceptions)

Usually, these professors hold a Ph.D from leading western institutions, and during their Ph.D they have published papers at extremely competitive top venues, like ICCV, ICDM, ICML and other places depending on their research interests. But, after returning back to Turkey and starting in an academic position, they can't even get their papers published in second tier venues.

So, what might be the reason for this ? If these people can publish during their Ph.D then why can't they do now ? Also, CS is not a field where extremely expensive lab equipment is required. So why are these people unsuccesful at publishing in top conferences/journals ?
The problem that faces faculty at second- (and lower-) tier institutions including those in foreign countries is that research is often not valued or not given the resources necessary to flourish.

For example, at many national universities  faculty have considerable responsibilities other than research, including teaching and national and local service. They may not have enough (or any) quality graduate students to help with teaching,  to inspire them to explore new research areas, or to conduct research together.  They may also have much more administrative duties with much less administrative support. 

Finally, there may be little incentive for them to do or publish research. They may have civil service salaries that are not adjusted for research output. External consulting or tutoring may be more lucrative than doing work within the university.