I assume it has something to do with the fact that anti tobacco lobbies, like truthinitiative.org after multiple crushing victories, needed a new target since they were becoming obsolete. Enter evil vaping. Instead of them embracing it as a potential tool for harm reduction, they decided that it was really nicotine that was evil all along.
Fighting about marijuana regulation really wasn’t their thing. They like to be one issue type of organizations; it makes them seem committed.
And though I agree with your general argument, it must be pointed out that nicotine is quite a harmful chemical, and is responsible for most of the heart disease people incur by smoking. Also, your assertion that vaping has less or less harmful nicotine is not necessarily accurate. Vape liquids come in many potencies, and unlike a cigarette, many do not offer a natural place to stop a session. A person may be vaping 3mg three puffs a day to control cravings, or they may be in their kitchen, taking down a fill of 9mg every morning with coffee.
Your personal experience with quitting is not likely to be typical in such an unregulated market.