There’s a common mistake to avoid when trying to gain internal support.
The mistake is to go to other departments and tell them how the community can help.
I know, this sounds like exactly what you should be doing.
However, in practice, this kind of unsolicited help is usually taken either as an insult or a threat.
It’s an insult because the person you’re speaking to considers themselves an expert. You’re effectively saying you have an idea for their domain they weren’t haven’t already considered (I know, it sounds petty…we’re only human).
It’s a threat if the community can help them do something they already feel they’re doing well themselves. Get off their toes!
The simplest way around this isn’t to tell them how the community can help, but ask how the community can help. Even if you know the answer, it’s good practice to ask.
Ask them for their advice and input into the community as well. What would they like to see? What advice can they give you? Let them see their ideas flourishing in the community (you didn’t take this job for the credit right?)
Now you’re not a threat and you’re respecting their expertise. Give it a shot.