Your existing staff were groomed over the years organically. During your expansion, your company did not have a system to quickly and adequately train your new staff to the required standard. Consequently, poor customer service led to poor customer experience. There was a lack of repeat business and sales slid back as a result.
You also found yourself lacking a capable new manager for your new business. While you have experience managing front line staff, you do not have enough experience selecting, training, and managing managerial staff. An incompetent new manager will lead to the failure of a new project. While many businesses tend to select and promote existing staff to become new managers, there is always the possibility that these staff may be promoted beyond their capability.