How internal Agile coaches are important when organizations want to increase their agile maturity?

Many transformations toward Agile are rolling back as soon the external experts start leaving the organization. Internal Agile coaches are the maintenance team and the living spirit of the agile mindset for an Agile organization and fundamental for the success. An organization profits most if they combine both. The responsible of the internal coaches is to manage the integration of the external coaches following this mindset.