The origins of business activity find themselves in a one man show with small local operations and small business size. The absence of technology also never made it possible for the small businesses to step out of the village ecosystem. Post industrialisation and technological advances the whole scenario changed and made is possible for businesses to expand beyond their local boundaries and serve a larger pool of consumers. This inherently led to expansion in the size of businesses to an extent the management of which by one man was found extremely difficult. This gave birth to an organisational structure in the management of business.
So today we have the well accepted principles of management which talk about the merits of work specialisation and division of labour which potentially lead to enhancement of productivity and efficiency in operations.
Each activity in any large organisation is departmentalised to bring in specialisation in function and thereby we have different functional teams who respectively do one specific type of activity in a focussed manner viz.HR, Finance, Sales & Marketing, IT, Administration, Production, Procurement/Purchases, etc. We find specialisation further down in each team where the broader function is broken down and specific responsibilities are given to individuals of each team. While all this is being carried out, care is taken to ensure that the larger organisational objective (shareholder value maximisation) is achieved. This is done through an integrated and co-ordinated approach through various levels of management and a hierarchy of managers who are delegated with responsibility and requisite decision making powers.
Thereby management by definition and nature is a group activity.