Such contests seem to be just a fun way to get students interested in algorithmics. Many of those who become passionate about Computer Science due to competitive programming go on to get PhD in CS and contribute with their research. Some highlights among Code Jam winners: Tiancheng Lou (won Code Jam in 2008 and 2009, went on to earn his PhD from Tsinghua University in 2012, currently start-up co-founder and CTO), Marek Cygan (won Code Jam in 2005, earned his PhD from University of Warsaw in 2012, currently start-up co-founder and CTO), Gennady Korotkevich (won Code Jam 8 times between 2014-2022, as of 2019 was a PhD student at ITMO University)
(sources: Wikipedia and Linkedin)
The first two have published some influential works during their academic careers:
https://scholar.google.com/citations?user=df8TSy4AAAAJ
https://scholar.google.com/citations?user=Vjo4Tg4AAAAJ
I wonder what the total number of research papers and citations of all Code Jam winners would be. Sadly, it's hard to find reliable info on most of them.