How is it anymore retro than other platforms that have the same games? Other than Nintendo arcade games.
The upcoming pre-Neo Geo SNK compilation is exclusive, the Japanese Seiken Densetsu collection is exclusive, the Johnny Turbo Data East arcade games are exclusive, Sega Ages is exclusive, plus Nintendo's own games are going to show up eventually, so there is actually a disparity between Switch and other platforms on that front. (Of course, they have their own exclusives.)
The hardware isn't inherently better for retro games but the publishers of these games say people are overwhelmingly buying them on Switch, as are developers of retro/throwback games. People want to play these games on Switch for whatever reason, be it portability or just nostalgia.