Cloud-based deployments provided the ability to provide elastic resource capabilities. This has several technical and cost advantages. However, from a business perspective, it opened up the possibility of a "plug-in" functionality that did not have to be developed in-house.
This was a tremendously liberating aspect for the business, and its impact is similar to the dawn of the Internet age. You could now browse for functionality that was required, and pay-per-use for the same. Using middleware, this functionality could be integrated with back-end systems. It is this empowering of the business that is now fundamentally changing the ERP space.