It's always interesting to see the DS vs Switch/PS4 comparisons, as both of the latter actually tracked ahead of it for quite some time, in spite of the former going on to pass 150 million lifetime.
Only at 26 months did DS break ahead of Switch; would that happen to coincide with the DS Lite by any chance?
DS Lite was more like ~18 months after launch (varies slightly by region) but yeah that was one of the key turning points for DS.
It was kind of a snowball effect though (using US dates, again varies by region)
Mario Kart DS-Nov 2005
Animal Crossing: Wild World-Dec 2005
Brain Age-April 2006
New Super Mario Bros-May 2006
Nintendo DS Lite-June 2006
That 10 month window saw a bunch of huge releases that helped expand the audience of DS.
When the herd loses its way, the shepard must kill the bull that leads them astray.