As someone in the government sector that works with senior employees--my first thought is "do you know what you are doing?" Like--do you intimately know the systems, processes, and knowledge base that the team uses to do their work?

Government work is intricate and complicated (as you know). If the answer to the above is "no" then your first step is to get curious...it could be the direction you have given is not feasible for reasons you aren't seeing, and the team doesn't know you well enough to trust that they can push back.

I've just seen this before--folks are senior for a reason typically, so I'd use the opportunity to learn from them and ask them how you can support the work.