The caveat pointed out in the next paragraph might help explain the numbers:

"Those numbers are complicated by the fact that Tesla vehicles weren’t counted in the study. Fully 75% of the EVs sold in the U.S. last quarter were Tesla products."

The anecdotal experience I've observed among friends is that Tesla owners are happy with the Supercharger network and better software, while other electric makers still are figuring it out, lots of buggy software, slow charging, etc.