Tutorial : Why do we need methods?

1.The author of the above article notes that “the development groups were isolated from one another - one group was doing analysis, one group was doing software design and a separate group was doing implementation”.
Why would this arrangement be a recipe for disaster?

When the development groups were isolated one another , how can they share information of part they do like analysis, software design, implementation . They cant connecting together how one group can discuss to other group . One group was doing analysis they have many idea to do project make it very interesting and unique but this group cant talk to group was doing software design that means group was doing analysis is useless because all of their ideas can't share to group doing software design , group was doing software design need find their own ideas to design software.And a group was doing implementation still need find their own ideas to completed project. I think if the development groups were isolated from one another, each group just do different project. One group unrelated to another they can completed project easier and less make mistake than when group were isolated from one another. The development groups were isolated from another this arrangement is really to be a recipe for disaster.