Hi,
These are in fact two different things.
On the one hand, with more people involved in the bitcoin community, chances get higher that business models are developped, making bitcoin useful even in everyday life, for daily shopping and so on.. This is one advantage of getting more people involved.
But this word is important: involved. If there are many people merely trading bitcoin for short-term profits, then it doesn't make the community stronger.
And last, on the other hand, bitcoin can collapse even though 1 human being out of 2 on the planet has a wallet. Banks can disappear even though they have many customers, it is just the same here.
In order to make bitcoin sustainable.. well you have to act accordingly. Avoid short-termism and think broader.