In every state that it's been legalized in, weed is heavily regulated. Weed must be tested for adulterants, heavy metals and mold contamination before it is sold. Some states even regulate the amount of active compounds that are present in the marijuana.
In the states I'm familiar with, it's also illegal to package, market or sell marijuana in manners that might entice children to use it. Sometimes that means banning THC laden candies or vapes that children can recognize, and banning the use of colorful advertising or cartoons, as well.
Cigarettes are sold at every convenience store in flashy packaging. They are made by deep-pocketed multinationals with generations of lobbying experience.
Legal marijuana, on the other hand, is sold with minimal advertising in licensed, purpose-built stores. If you gave tobacco companies a choice between banning menthol and forcing the sale of cigarettes in tobacco stores only, I think I know which one they'd pick.
It was, and still would be extremely unpopular. The public health reason is as strong as it's ever been.
It became extremely unpopular when it became law, and people found out what this actually means - a large black market for organized crime to cultivate, and heavy-handed enforcement with plenty of "collateral damage".
There's no evidence it ever had majority support, though: https://www.vox.com/2015/10/19/9566935/prohibition-myths-mis...
The campaign was effective at getting an unpopular law passed. I think that's how we should read prohibition.
Besides which, we don't have to go all the way to prohibition to make a dent here. A pigouvian tax would be good enough to start with, and maybe better education on the effects of alcohol.