They may be laymen on the subject, but they heard the evidence and expert testimony...that makes them more knowledgeable about the facts than anyone in this thread, and yet you’ll see many educated people here with opinions without any facts (beyond newspaper articles).
And while they may be better equipped to make a finding of fact of a criminal case (did person x do y), but often it’s still just a chance they get it right, plus those criminal cases have a much higher standard than a civil case.
So it’s important to keep in mind what is being asked of the jury here. They aren’t asking if roundup cause cancer, not even asking did roundup cause cancer beyond a reasonable doubt, but simply based on the expert testimony and facts presented is it more likely than not (>50% chance) Roundup caused cancer.