I'd say the Apple Newton in 1993 made touch screens mainstream quite a bit earlier. And things like PalmOS were clearly based on the excitement that came from the Newton. The Newton itself wasn't that successful due to its reliance on writing recognition that didn't work that well (at least in the initial versions of NewtonOS) but that ironically added to its place in pop culture. Like in The Simpsons where one of the school bullies has a Newton and is trying to take a note reminding him to beat up the annoying teacher's pet Martin, only for the system to interpret "Beat up Martin" as "Eat up Martha".

It had a resistive touchscreen. What made you touchscreens truly mainstream were capacitive screens

Yeah, touch was a total joke when the DS came out. It was ridiculed as a useless concept.

Just a few years later and people are more confused when their device has buttons instead of a touch screen.