I would think that Brown knows he is not good enough to be the #1 guy on a title team. Very few players are, this is not a knock on Brown. Unless he wants to be Bradley Beal, the best player on a mediocre team, he is not going to be "the guy". And as I said, it seems to me that Brown is smart enough to understand this.
I don't believe this is how most players think about this - about moving teams to prove you can win a titles as a #1.
I believe it is more about (1) I am good enough to do more than I getting an opportunity to do on my own team. To proving yourself capable of doing more than you are already doing. In some cases, of being more than a robin to somebody else's batman (2) opportunity to earn more money via NBA paycheck or sponsorship deals (3) more media attention and accolades for accomplishments. Sick of being overlooked / looked past while other players garner all or disproportionate amount of attention. Don't feel they get their own just deserves (4) having a team built around you both in terms {a}maximizing myself {b} respect / kudos from rivals that you are a legit franchise guy. And that respect from peers / competitors you get when you are the franchise guy of your team instead of a supporting piece.
And then it is ... the start of a new adventure. See where it takes you.
It is about proving you can be a #1. You can be the lead dog; the main man. The catalyst for your team. The guy the team is built around. Then comes the focus of individual success ...
But team success is further down the line and it usually starts with winning lot of games before turning into hopes of winning a title after a couple of seasons when the shiny new things (money, fame, awards) start to lose their shine and you begin focusing more on long term legacy / titles.
Winning a title / team success is rarely the starting point. Individual success / money / fame / credit / proving oneself are.
"Being good enough to be a #1 on a title team" -- I just do not think this is how players approach / frame the idea / decision of whether to leave a team or not to prove yourself as a franchise guy.
It is more can I be as good as Devin Booker more so than can I be as good as LeBron James. Can I be as good as Carmelo Anthony more so than Tim Duncan. Seeing guys of somewhat similar ability who get more media attention, more sponsorships and money, more awards and recognition from the media.