Let’s not overthink Brian Roberts‘ rationale for engineering Comcast‘s $45.2B all-stock deal today to buy Time Warner Cable. I don’t think he did it, as some observers say, primarily because he’s concerned about the falling number of cable video subscribers, the threat of competition from phone and satellite companies, or to help resist rising programming costs. Roberts pulled the trigger because he could pick up some of the country’s most important cable systems — including Manhattan and parts of Los Angeles — without having to write a check. The deal will be virtually tax free. And his power will be secure even after TWC shareholders own 23% of Comcast’s Class A shares. Roberts controls the company’s Class B shares which have 15 votes apiece, enabling him to cast a third of all votes. The deal was almost a no-brainer: Roberts keeps Charter Communications and its largest shareholder, Liberty Media’s John Malone, from becoming rival industry powers. And he scores TWC’s 11M subscribers, 52 news and local programming channels (including New York’s NY1), and two regional sports networks in Los Angeles. In addition to NYC and LA, TWC has substantial franchises in large markets including Dallas, Kansas City, Milwaukee, Cleveland, Cincinnati, Buffalo, Rochester, Hawaii and most of the Carolinas. They complement Comcast’s holdings in Philadelphia, Northern California, Houston, Minneapolis, Boston, Seattle, and Miami.