Why has project management become a dominant management science over the past few decades?

There are probably three main reasons for this, but probably a lot more secondary reasons: (1) Things in the world are becoming ever more complex to procure/make/assemble, and with complexity comes some type of management to make it all possible; (2) Money or funding - people and organisations in this competitive world can't afford to overspend delivering projects, otherwise they would be soon out of business. Contracts are becoming ever more detailed, and there are now clauses in a lot of them about liabilities and who pays if things go wrong; (3) People - projects and programmes are all about getting people together to do work in a coordinated fashion - there are a number of tried and tested techniques and processes to make this all happen. Don't reinvent the wheel, why not use the best practices and procedures that project management has already developed.