Cryptocurrencies are like celebrities as you are trying to put it. They need to be relevant to stay afloat in the market, they need public attention for people to engage in them, and once they served their purpose, there's no telling what the future will be for them. But unlike celebrities who only rely on shows and appearances to remain relevant, cryptocurrencies can remain relevant for the years to come either by remaining in the market as a powerful contender, as in the case for bitcoin, or implementing a very functional design and project right at its conception that could fill the niche that the market needs.
Bitcoin advertisement or promotion by celebrities are always good to make people interested in bitcoin but the most important thing is the acceptance by governments or everything that will ease people to use bitcoin. Today there are many countries start to accept bitcoin, if government accept bitcoin then bitcoin related company will grow easier. I think the news that we need is bitcoin acceptance by governments.
I don't think that's what OP meant by the post, but let's assume influencers and celebrities do invest in bitcoin and shill it in their respective platforms out of pure support for the cryptocurrency, they will leave a bad taste in people's mouths when bitcoin dumps in value, which is definitely not good for their career as they rely on the public's good interest for them to receive projects, this doesn't happen with bitcoin and any other cryptocurrency for that matter.