There is evidence that some additives enhance addiction and that others suppress the side effects from smoking (coughing, burnt throat, feeling ill, etc.) so that when someone quits smoking they have essentially stopped treating themselves for all these side effects, which then appear and make the person feel miserable. Smoking instantly relieves symptoms again (for a while):

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2040350/

"Our findings indicated that more than 100 of 599 documented cigarette additives have pharmacological actions that camouflage the odor of environmental tobacco smoke emitted from cigarettes, enhance or maintain nicotine delivery, could increase the addictiveness of cigarettes, and mask symptoms and illnesses associated with smoking behaviors."

So it appears that although nicotine is mildly addictive, commercial tobacco was engineered to suppress the side effects of smoking which essentially made it much more (technically) addictive. Hence quitting tobacco is much more difficult than quitting nicotine because you are also quitting the additives which are suppressing cough and hiding the feeling of illness smoking causes.

Here's one: https://www.jneurosci.org/content/25/38/8593

Abstract:

Nicotine is the major neuroactive compound of tobacco, which has, by itself, weak reinforcing properties. It is known that levels of the enzymes monoamine oxidase A (MAO-A) and MAO-B are reduced in the platelets and brains of smokers and that substances, other than nicotine, present in tobacco smoke have MAO-inhibitory activities. Here, we report that inhibition of MAO dramatically and specifically increases the motivation to self-administer nicotine in rats. These effects were more prominent in rats selected for high responsiveness to novelty than in rats with low responsiveness to novelty. The results suggest that the inhibition of MAO activity by compounds present in tobacco smoke may combine with nicotine to produce the intense reinforcing properties of cigarette smoking that lead to addiction.

There's research that the heat alone in some forms of abuse of smoking things can cause lung issues.

The difference I've found with vaping is both a) I use a very cool setting so it's not nearly as hot as a cigarette (which you can't control the temperature of) and b) I used far less nicotine, starting from 24mg->3mg in the course of a year.

I can easily stop vaping for days at a time now without having a strong pang of nicotine dependency which I used to have.