When talking about agile and agility, we should not forget that we are talking a lot about culture, values, and identity.
Irrespective if you start from top to bottom or from bottom to top, we need to understand that we have to take a lot of people with us. For many it is a big adventure, as their system, which helped them to achieve stability and reliance is questioned to some degree. We ask them to trust people, with whom they probably never have worked with and where they are lacking a fundamental understanding of their needs and objectives.
I am trying to change an organization from a kind of middle layer for almost one year now. In this time I had to learn several things. The first thing was to have the right intentions. From a point of view, where we have a pretty good idea of what might be required, we tend to be too ambitious to drive change. We want people to think differently without giving them the chance to understand what it is all about. Set free a domesticated animal to the wildness, and it will not feel free but frightened. You need to get used to a different kind of thinking and acting.
The second learning was about the importance of humility. Understanding that people have to learn, requires a good amount of patience. The guys need to have time to fail and to learn from it. They are not dumb, but they do not start on a greenfield. Humility can help a lot in supporting them to change their minds, as they need to do it on themselves. Steady feedback is a very important instrument, that will do wonders in such a context, as it helps to consolidate understanding and recognize even small changes.
Finally it is about trust. At first, you need to have a lot of confidence in your vision and objectives. It is something others will feel. You will not have to talk about it. Moreover, have trust in others to create the same kind of confidence. With the growing understanding, the steady feedback, and a good amount of time they will follow up. The trust you put in them will make them feel they are on the right way.
So if I want to summarize it, modern agile methods will provide tools to steadily work towards an culture, values, and identity to face the volatility and uncertainties in our world with confidence from mutual understanding, feedback, and trust. This definition does not have to consider a top or bottom anymore.