It's not free advertisement because the man is courting the people for support. As well as donations, of course. By clearly speaking out his stand in favor of Bitcoin, he's certainly hoping that the community that is also in support of Bitcoin will rally behind him. This is elections season.
Anyway, quite similar to mk4's question, why "as a collectible" when Kennedy Jr. has probably not even once called Bitcoin as a collectible? He called Bitcoin the "perfect base currency," an "exercise in democracy," and others but not as something to be merely collected.
How many Bitcoiners are US citizens? Several million? Not a big enough number to win the elections, if you ask me.
I remember that in the 2020 US presidential elections, another candidate from the Democratic party was pro-Bitcoin, but he got a ridiculously low amount of support. I even forgot his name. Stating that you are pro-Bitcoin doesn't mean anything. What if a republican candidate also declares, that he supports Bitcoin? I think that Ron DeSantis also made some public statements in favor of Bitcoin/crypto.
Most crypto supporters are right wing libertarians, so I doubt that they will support a left wing liberal/socialist candidate.
I don't know how many Bitcoin supporters in the US. But does it have to be several million for candidates to try to win their votes? Does Kennedy Jr. court the support of the Bitcoin community because it will make him win?
Anyway, accordingly, "about 46 million Americans (roughly 22% of the adult population) own a share of Bitcoin."
[1] I don't know whether this is true or not but my point is, in an election season, all communities, big and small, suddenly matter. Candidates utter sweet words in front of everybody: Asian Americans, Hispanics, black Americans, senior citizens, LGBT, gun owners, farmers, American Indians, Catholics, war veterans, baseball fans, Bitcoin supporters, and so on.
[1]
https://explodingtopics.com/blog/blockchain-stats