句中完成时的使用方法

The research for explanations in the many post-mortems of the crisis has meant blame has been spread far and wide. Governments, central banks and auditors have all been in the frame. The role of bank directors and management and their widely published failures have been extensively picked over and examined in reports, inquiries and commentaries.

这是雅思考试真题中的一段话的相邻的几句。求指导为何都用的是完成时，使用方法分别都是什么呢？

谢谢回答

目前完成时表示不确切的过去时间发生的事件，或过去事件对目前的影响。这几个句子谓语都没具体的过去时间状语修饰，为不确切的过去发生的事件。说话人不关心过去，而是关心目前，所以用目前完成时。