People are at the heart of development. They are the ones to come up with creative solutions, make difficult decisions, continuously scout for risks and how to counter them, etc. Sometimes working by themselves, but mostly working in an agile team where 1+1>2 but not always so easy for the different specialists and challenges like lead times.
And of course the team is not in isolation, it’s an integrated part of an organization with all kinds of stakeholders like customers, the business, operations, suppliers. For hardware there is usually a lot of interaction required between development and operations (also know as DevOps), and suppliers. For details see the article on DevOps and Suppliers.
Trying to build a complex physical system in a complex adaptive organization is challenging. To make this work, we need strong leadership with the right competences (knowledge, insights, skills, attitude/mindset).
Whatever you try to develop and build, there will be some rules to adhere to. Sometimes, they are valuable lessons learned collected in for instance design guides, sometimes more strict rules like company regulations and procedures. Sometimes from the outside world like machinery directive or medical device compliance. There are several good practices to deal with compliance in agile hardware development. For more information see the article on compliance.