I think there’s some nuance here. You can’t totally prohibit something people really want to do, but you can pretty effectively prohibit something almost no one wants to do or where there is a very good substitute.

Having a tiny landmass, and no land borders also helps. It’s possible to grown tobacco hydroponically but I’m not sure if anyone would bother unless there was an overnight hard ban.

Nicotine is still available to the younger generation in the form of vapes. It isn't a strict prohibition, it's an effort at harm reduction by turning people away from the worst method of ingestion. And, yeah, time will tell.

It will not.

They will see the microscopically minuscule number of people who still smoke due to the black market and claim the entire effort to be an abject failure.

They will ignore the millennia of higher quality lifespan added to the population, the massive savings in public healthcare expenses, and the almost-non-existent second hand damage smoking does and just focus on the thousand or so people smoking smuggled cigarettes.

When you suggest that their position is somewhat analogous to not passing laws against murder because "well that dude over there got murdered so OBVIOUSLY the laws aren't not working" they will just look at you funny.