It might come as a shock when existing influencers and leaders within your topic's ecosystem don't join and support your noble community efforts.
It's easy to understand.
If you're an influencer, it's likely the existing ecosystem works well for you.
Every new entrant is perceived as a threat to your power (power is perceived as a zero sum game).
You don't want to change the status quo if you benefit from the status quo. You don't want to help support others that might reduce your power.
This is why many sectors are dominated by a tiny group of highly influential people who support one another to maintain the status quo. Outsiders are challenged and denounced. Outsiders usually need to break through without their support.
Of course, you can ignore the influencers and build your own audience from scratch. Once you become big enough, they'll help you in the hope you reciprocate.
Or you can engage the existing influencers in a piecemeal way. You can interview them, offer them guest posts, and offer them a chance to use the community for further publicity. They might link to you and given you token support. But they won't do this until your community is important enough to make it worth their time.
The better solution is to offer them real power in the community – perhaps more power than you. You have to stitch together a network from the existing key actors within the ecosystem for the community to succeed.
This means giving them a real role in how the community is run – not token efforts.
You have to approach them with an offer of more power, not less. At times they will do something that you disagree with – that's the nature of community building. You get the joy of building it, but not authoritarian control.