Cheapest to insure
Many factors influence what you pay for car insurance including how you drive, where you live, how old you are and your gender.
What type of car you're insuring is another major factor, however.
Even that single factor isn't entirely straightforward. A car's influence on insurance premiums is largely due to the claim history of that car and ones like it. And that insurance claim history will be influenced by things like the way people who own that type of car tend to drive, where they tend to live, how old they tend to be and things like that. (That's why sports cars cost more to insure. They figure you're not buying that hot little two-seater so you can carefully obey all posted speed limits.)
In addition to all that, some cars just cost more to fix.
While the Cadillac CTS is the least expensive car to insure, the Chevrolet Tahoe is the least expensive SUV. Relatively large size helps since it means that a "fender-bender" is more likely to involve just the fender and not the engine or vehicle occupants. More sedate drivers probably help, too.