When you need more stakeholders involved, ask your main contact first instead of reaching out directly. Tell them that based on research, roles like finance, operations, and legal typically review proposals, then ask if those people should be included. Small businesses have one decision-maker; large companies use committees, and you need to address each member's concerns.
A pro tip here. I am not suggesting you bypass your main point of contact and reach out to other stakeholders directly. That is rarely advisable. People don't like to be circumvented. Here's one way I would address it with my main point of contact. I would say, in my experience, people in these roles, and then you list the roles that you researched, like management, finance, operations, and legal, Typically review proposals. I thought to check with you if folks in these roles here need to be looped in. The main thing is to remember that small businesses have decision makers, enterprises have decision systems. And if you don't map the full committee, address what they care about and what risks they're evaluating, you are pitching half a deal.
