The 3DS (and relatedly the Wii U) bombed because they had fatal, expensive gimmicks. The Switch 2 is a hardware iteration that everyone has been asking for.
Both also had a massive own-goal branding problem, in that nobody who wasn't a gaming nerd could figure out they were totally new consoles, not new editions of an existing one, from the name.
The 3DS had it even worse than the Wii U, since the DS line had several versions with very-similar names some of which were variants of existing ones, and a couple of which were actually totally new platforms (was it the DSi that was the other one? I can't even fully remember and I'm way farther down the console-nerd path than the vast majority of people)
At least they just put a number after this one, so folks will get it this time.
Most people I know that own a Switch use it rarely and casually. For them a mere hardware iteration isn't enough of a reason to get the new one. I would suspect that a good 60% of Switch owners fall into that category. However, even if it only gets half of the sales that the switch had, that would make it the most successful current generation console.
