My understanding of the study is it is highlighting that without good public infrastructure it is difficult for most people to go car free.

For example, for me, my daily commute is ~20 minutes each way by car. Or ~3+ hours one way by bus, ~5 hours walking, ~90 minutes biking. The closest store to my house is a 20-30 minute bike ride, or hour walk, without sidewalks or bike lanes for most of it, making it rough and dangerous to traverse (Dont get me started on how its an over 1 hour bus ride [yes for a route that takes 40 minutes to walk]) It is its own chiken and the egg, poor infrastructure is justified as not even enough usage but people dont use it because there is not enough non-car infrastructure.