Before Angular was introduced, the web developers used VanillaJS and jQuery to develop dynamic websites, but the biggest drawback of these technologies is that as the logic of the website grew, the code became more and more complex to maintain. For websites and applications that use complex logic, developers had to put in extra effort to maintain the separation of concerns for the app. Also, jQuery did not provide facilities for data handling across views.
The client-side frameworks like Angular were introduced to overcome the above problems. It provides developers many benefits over VanilaJS and jQuery by providing a new feature called components for handling separation of concerns and dividing code into smaller bits of information.
Client-side frameworks such as Angular facilitate developers to develop advanced web applications like Single-Page-Applications. So, the main reasons behind introducing Angular were to create fast, dynamic, and scalable web applications easily.