A couple of points. Independent CRNAs tend to practice in one of two settings- Rural areas or physician offices or low level surgicenters, e.g. endo suites, cataract centers, etc.
Rural area residents tend to be people who tend to be more of a "self reliance" crowd and disinclined to put a bullet in what is frequently one of the town's biggest employers and only health care option for them and their families-The local hospital and its staff. Hence they are not good juries for the Plaintiff's bar.
Physician offices and low level surgicenters tend to have soft ball cases where risk is exceptionally low.
CRNAs and other midlevels who work under MDs in hospitals that tend to have restrictive bylaws which mandates that they work only under the supervision and control of the MD . This is a significant liability shield for the CRNA who works in an ACT setting who makes a bad decision that results in a lawsuit. It may be the CRNA or other midlevel's FAULT, but it is frequently the RESPONSIBILITY of the MD.
This is one of the AANA shrill cries, that malpractice premiums for CRNAs are frequently the same or less than for anesthesiologists. In their argument, because there is no difference in level of care or bad outcome. The above are the real reasons for the lack of significant disparity between anesthesiologist and CRNA medmal premiums.