Its hard to see details from that one picture but it looks like a handyman’s attempt to install a radon mitigation system. I’d try to find out who installed it, and when? Any information you can get. Big thing I noticed it is missing the vapor barrier which is a very important part of a crawlspace mitigation system. Personally, I think I would recommend a retest(because obviously it had high radon prior to the install) and the reason being is because: there appears to be a Radon “like” mitigation system present, however the system appears to be “handyman” installed which brings into question the functionality of the system itself. If the test results still come back acceptable it is up to them if they want to leave it that way or have a proper mitigation system installed, but I’d still call it out either way.