Training drives the successful adoption of the new system and processes. The learning capacity of the audience and the amount of changes being introduced to them dictate the amount of time you need to spend on and retraining. The more people you have up to speed on the new processes and system, the smaller are the chances of them making mistakes, and the volume of support calls will be highly reduced. Ultimately, this results in a smoother adoption of the new system.
The ERP project is an opportunity for organizations to get people up to speed on end-to-end processes and train them on cross-functional areas. If you have a great system designed but people are not able to use it, can you call it a success?