Yes a small competent team could build the IT system for a fraction of the time and money. However they would only be successful if the business processes were well defined which I'm willing to bet they were not.
New IT systems often come along with changes in process, a well defined IT project should produce a system that follows and complements those processes. Instead what we often get are "boil the ocean" projects that attempt to fix process issues under the guise of an IT implementation.
^^^ This! I was involved on writing an invoicing system that ended up failing. The real intent of management was to try to bring more control to pricing using the project. Management was unable to negotiate this new process, so it ended up being an overpriced spreadsheet and was replaced a few months later when the company switched to Salesforce.
New IT systems often come along with changes in process, a well defined IT project should produce a system that follows and complements those processes. Instead what we often get are "boil the ocean" projects that attempt to fix process issues under the guise of an IT implementation.