I've written before about MO and IQOS. It's a complex issue, but here are my beliefs.
MO was always in a tough position when in comes to next generation products. They had (and still have, although diminishing) a huge US market share in both cigarettes and moist oral tobacco. Their overall market share in both segments was nearly 50%. The other half of both those segments that their competitors own, is majority discount. So if you look at purely the premium market for sales of cigarettes and moist tobacco (which is where nearly all the profit is made), MO's share is close to 70% in cigarettes, and over that in moist oral tobacco.
The FDA does not allow marketing next generation products to non-tobacco users. Likewise, with widespread publicity about health issues and regulatory bans, there are not a lot of new users taking up tobacco usage. So where are the customers for heat not burn, vaping, and modern oral products in the US going to come from? Answer: heavily from current Marlboro and Copenhagen users.
PM was in a different position. Yes, they had some countries where they too dominated the cigarette industry with Marlboro cigarettes. But they had many countries where they had a minority of the cigarette market. For example, in Japan, PM had about a 25% market share in cigarettes prior to the introduction of IQOS. That left 75% of the market to go after and take from a competitor, rather than cannibalizing their own sales. In the UK, they had only about 2% of the cigarette market, so nearly every new IQOS user there comes from a competitor. It is a lot easier to introduce a new product in those circumstances, versus when you have a near monopoly on the product you are trying to replace.
Making the situation even worse, since MO never wholly owned either IQOS or JUUL, they were going to have to split the profits from those sales, versus them keeping the entire profit from sales of Marlboro and Copenhagen.
Which is logically why MO has never really promoted an end to cigarettes like PM has. Doing so would likely have meant significantly lower earnings over the short term, and no guarantee of higher earnings over the long term. In fact, there are few scenarios where they will ever make more money on next generation products than they do on cigarettes and moist tobacco today, even if they fully own the IP of the next generation products.
Which is why MO has increasingly turned to regulation to maintain their position. They are actively petitioning the FDA to ban most products, and for the FDA and local law enforcement to remove unapproved competitors products from the marketplace. And while they publicly support safer products, it is very unclear to me if behind the scenes, they aren't actually lobbying to restrict them, tax them highly, and spread uncertainty about their health benefits. There are other political and monetary factors, but I think MO is a major reason why the US is far behind many other countries in adopting these products.
Nevertheless, even MO knows that change is inevitable. The reason that they bought NJOY is because they fully own and control it (unlike JUUL), it already has FDA authorizations, and vaping is taxed at lower rates than heat-not-burn is in the US. That is because most current excise tax laws treat the actual tobacco sticks found in HEETS the same as cigarettes, including being liable for MSA payments. I'm sure they are hoping to hamstring and keep IQOS down through those higher taxes, as well and lobbying and marketing ploys to create confusion and doubt.
So it isn't going to be easy for PM to grow IQOS in the US, but I think that it's worldwide success is pretty good evidence that MO is going to struggle to defend against it. Just as Zyn has carved out a big chunk of market share previous held by Skoal and Copenhagen, I think over the next 5-10 years, IQOS will do the same to Marlboro in the US.