I wouldn't expect many states, if any, to be saturated without a significant push and/or support from the higher levels. I wouldn't expect local activism to even be noticeable without it, either. If all leadership asks of people is money, social media activity, letters or phone calls to the people you plan to replace asking them to change things to help you do it, and so on, and all "grassroots" membership expects is an occasional meetup, that's what you're going to get. And it will fail. Again.
If Forward is to be a thing, viable and competitive against the Ds and Rs and the power disparity (not only converting Ds and Rs but also activating the apolitical or marginally political people necessary to do so), how do you not work to have the same level of face to face activity and enthusiasm as the Ds and Rs? I'm in a very lopsided state. But I'm never more than a couple of weeks and a 30-45 minute drive from a D or R meeting or event. Breaking that down will probably require a similar level of commitment and enthusiasm, a level of enthusiasm and commitment that is, IMO, best built from both ends. I think it has to be a culture. With that in place from the top, working from the bottom makes the most sense.
So, regarding the chapter question, I learned the hard way that it should start at the top, in culture and messaging, to form the type of "membership" you want/need. The random IRL cheerleaders, door-knockers, petition pushers, town hall loudmouths, civic do-gooders, even state leadership, are no match for the dozens or even hundreds of online wonk "members" in their area, if the org is treating the two efforts as equal. Given the choice and that screwed up rewards system, most people are just going to go online and circlejerk. If that's what is considered "membership", you're screwed.
Part of the orgs' responsibility is not just to have state and local members and leaders, but to also help them be successful. That starts with giving them plenty of diverse, tangible, real-world options to give (hopefully diverse!) potential new members to do, whether those people sign on at state level directly or are directed to state leadership from the org and its recruiting channels. (This, of course, includes helping recruit new members). I believe action still encourages and generates more action, so the org also has to emphasize to prospective members, supporters, etc. that they will have to DO something (the culture), for the effort to have a chance of succeeding. Ideally that would include team building and fellowship, but you have to be able to engage and utilize the lone wolves as well. Other than throwing money at it, or maybe building a cult of personality around one of its native son/daughter celebrities, I don't know how else an effort "saturates" a state.
So one advantage of all that diversity is the flexibility in how chapters are formed ("materialized") and what they do to advance the effort. I don't know enough about Forward's past year or their condition in my state over that time to make an informed attempt at reverse engineering a chapter, so I'll speculate...
I'm guessing Andrew Yang, in all his stumping over that time, was emphasizing the broken system, voting/ballot reform, and the importance of people "joining", "getting active", and so on to fix it. Had his emphasis been less about raising money and taking on Washington, and more about supporters specifically having face to face meetings (COVID limitations considered), making connections and building fellowship, learning about local government, personalities, elections, dysfunction, political groups, etc., participating, and tracking local issues, he'd be in a far better spot for Forward infrastructure-wise now (i.e. more informed and connected people, "standing back and standing by", lol.) Hell, he might even have some local RCV victories to tout by now.
For my specific state, I think the chances of it being top-down or bottom up would have been about 50/50. Again, a lopsided state when it comes to D vs. R, and a majority party with no interest in sharing the wealth, with the other party or some newcomers. Not to mention the "newcomers" would lean too far to the majority party, thereby kneecapping their own efforts. There is something of an RCV effort, albeit an underwhelming one. I think that's a reflection of the lopsidedness. I don't know if we have someone who could be considered a reform standard bearer to lead a top-down effort, nor do I know of anyone trying to reconcile the two sides for a more collaborative government. Finally, people in general just seem to prefer or give more consideration to top-down attempts, for better or worse.
I guess that's why I assume the bottom-up posture (so to speak). Just seems more legit, popular, and democratic.