For Comcast, taking control of NBCUniversal will complete its transformation from a content distributor by way of cable and broadband networks to a fully-integated media behemoth that also owns top broadcast, cable TV, film studio and theme park assets.

Such a move continues to differentiate Comcast from cable peers, while putting it into closer running with content creators like Disney ( DIS), CBS ( CBS) and Time Warner ( TWX).

The deal may also reflect improving operating results that make a large stake acquisition opportunistic given expectations of continued growth.

In 2012, NBCUniversal revenue rose nearly 13% to over $23 billion in annual sales, while operating cash flow grew over 9% to $4.1 billion.

"We are excited about the future prospects of NBCUniversal," Roberts said on CNBC. "Our shareholders have 100% of the upside here," he added.

Such sentiment mirrors similar commentary from Morgan Stanley chief executive James Gorman in explaining a far faster-than-expected planned acquisition of the bank's brokerage joint venture with Citigroup.

"After a year of significant challenges, Morgan Stanley has reached a pivot point. We demonstrated meaningful progress in our Wealth Management Joint Venture, reaching the highest pre-tax margin since the inception of the JV," Gorman said, in January.

In fourth-quarter earnings, Morgan Stanley also showed long overdue progress on the brokerage unit's profitability. Net revenues were $3.5 billion and pre-tax margin rose to 17%, far above the 10% that had raised some investor and analyst alarm in past quarters. When the brokerage JV was cut, Morgan Stanley forecast 20% margins.

On news of the deal, Comcast shares rose over 7% to $41.71 in after-hours trading, a new record high for the company. General Electric shares gained nearly 3% to $23.21, reaching a five-year high in after-hours trading.

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