I have learned one thing through three home purchase and two sales; there's no leverage for realtors to represent you in your best interest. Take an inspector for example. A thorough inspector might ruin a sale. They'd then not be recommended by the realtor again thus hurting their ongoing business. So, at the end of the inspection the home buyer is NOT getting the best inspection. We were screwed when we bought a house in MN. And we were screwed again on different issues here in WV. When I confronted the inspector about whether they evaluated the attic insulation, their comment was "according to WV inspection codes we don't have to do it for house less than 5 years old". Geez. All they needed to tell me was what depth was up there and let me decide. Sadly, our society is leaning towards lies to gain business.
Your radon situation is another one of those where they'd just assume convince you someone else will buy the house without any radon mitigation. Our new home purchase here in West Virginia was faced with radon levels of 14. It's a brand new house with zero radon consideration. The ideal situation is a perfectly sealed basement floor. The next best option is to use an interior drain tile with a sump pump seal. Of course, we'll have to bore holes in our 'finished' basement floors. Until then open windows venting out has reduced it to ~3.