Even if you combined the two Link's Awakening releases from the 90s (which, to be blunt, I think would be daft given they are clearly two different releases of the game), you're looking at 6 million sales achieved over a period of what, 6 or 7 years? Whereas the Switch release will manage that in half the time at most.
It's true, I think, that Breath of the Wild proves there's a market for open-world Zelda more than massively growing the market for Zelda, but the important point there is that by hitting 5 million plus, the other two Switch Zelda titles are hitting territory the franchise rarely ventured into before Switch. It's practically guaranteed that both Link's Awakening and Skyward Sword will shift over 6 million - LA's 5.49 million figure is now 10 months out of date. For Skyward Sword HD, we only have 2 months of sales. But when you look at the overall context for Zelda on Switch, then yes, I think Breath of the Wild has absolutely boosted the series' popularity generally; it's just that Breath of the Wild itself is still massively more popular than classic Zelda.
Look at it this way - before Switch launched, only 4 Zelda titles in 3 decades had crossed the 6 million mark (the original in 1986, Ocarina of Time in 1998, Twilight Princess in 2006, Ocarina of Time 3D in 2011). Those milestones were few and far apart. On the other hand, the odds are extremely high that, by March 2023, we'll have had four Zelda titles sell more than 6 million units each in a six year period - Breath of the Wild (2017), Link's Awakening (2019), Skyward Sword HD (2021), Breath of the Wild 2 (2022). It will also remain true that, while Link's Awakening and Skyward Sword each sell somewhere around 6 million or so, the two Breath of the Wild titles will sell far better than other Zelda games.
Ultimately though the series is more popular now than it ever has been, though Breath of the Wild, and the particular style and world of Zelda that represents, is much more popular than the classic style. But the classic series is selling more copies than before and it's doing so in a short period of time. The two classic Zeldas on Switch (so far) will outsell all but 4 or 5 of the 20 odd other Zelda titles, and 2 of the games they don't outsell will be open-world Zelda games.