As an ecosystem leader you must ensure that your ambition to establish an ecosystem is credible. It is not sufficient to announce that you will build an ecosystem.
Your partners must believe that you are willing to let go, to let them have a share of the value that is created for the final customer? Your claim that you want to build an ecosystem must be backed up with tangible commitments to share some of your knowledge and capabilities.
This may be difficult for large established companies with a track record of acquisitions and internal development. It may be difficult to avoid that their intention to start an ecosystem looks like a disguised attempt to start up a traditional supply chain.
But there are examples of incumbent companies that have established such credibility and started a successful ecosystem. Examples are Thomson Reuters (now Refinitiv) or The Guardian.