Why do you think agile is so popular?

The agile development methodology has received wide attention since it was proposed, even those organizations that have been concerned about the non-light-weight field, such as IBM/Sei. So why? We all know that the existence of everything is justified. In this case, the existence of agile also has its own reasons. So what is it?
First of all, from the historical background of agile, when Agile was not born, many people were discussing the software process, especially the heavy software development process, these software development processes are either waterfall-type or waterfall-type plus iterative methodology. It is obvious that these development processes are inherited from the waterfall development process to varying degrees. We know that the waterfall development process is a typical top-down development process. The methodology inherited from it naturally has such characteristics. However, the top-down methodology is often not in line with the reality, and too many streamlined things are not easily accepted by developers, of course, the author of such a development process is often not a front-line developer. All in all, these top-down development processes are too bureaucratic and are not welcomed by developers.
From the characteristics of most projects, many projects are not as clear as they are at the beginning, and they can be completely divided into modules with clear boundaries. On the contrary, projects often start out of chaos. Obviously, it is inappropriate to apply the top-down approach to such projects. Therefore, many projects are implemented in a bottom-up manner.
Many of the creators and advocates of agile are front-line developers who have a deep understanding of the features of most projects because they want to find a development process that truly belongs to the developers themselves. So agile came into being. At the beginning, agile only proposed some dynamic program and some best practices. Slowly and slowly, more people joined the agile team. After deepening their understanding and in-depth practices, they invented development methodologies such as scrum and XP under the guidance of agile, and added more best practices for agile. In short, the Agile Methodology emphasizes bottom-up software development, best practices, and release developers from documents and processes.
Through the comparison above, it is hard to know that agile development methodology has exhausted the time, people, and combined with reality and people as "one". I think this is why it is so popular.
If it is in line with the development rules of things, new things will gradually replace old things.
Agile is such a new thing that conforms to the current trend of software development methodology.
However, agile also has some limitations. It is not suitable for situations where the team is too large and it is not suitable for situations where there are already detailed requirements, and so on.
Therefore, many organizations are not simply agile, and have integrated references to agile and other heavy development methodologies such as RUP/cmme. Why?
I think most projects seem to be bottom-up, but software engineering is software engineering after all. It has some basic characteristics of engineering, that is, unified organization and management, therefore, from the perspective of organization and management, it is top-down. Therefore, when building our own development process, we need to integrate agile and RUP/cmme.
Therefore, I believe that the combination of top-down and bottom-up is the trend of future development methodology.