I have no inside knowledge of the Red Sox organization, and would defer to those who do, but I would like to add three observations:
1. Well-run organizations seldom delegate important decisions solely to one person; good managers are expected to elicit input from above and below and generate consensus. It was never clear to me whether Theo - Larry tensions were about a micromanaging superior or a subordinate chafing that the next rung on the ladder was occupied.
2. Theo managed to land a job in Chicago which is not only equivalent to Lucchino's but includes far more influence over baseball ops than Lucchino ever exerted. Theo is a very ambitious man, and such men seldom succeed without a touch of ruthlessness.
3. There have been far more negative things leaked to the press about Lucchino than anyone else in the Red Sox FO. It's really unlikely that he was ever the primary source of leaks.
And a comment on the Beckett trade, which may be the defining moment of Lucchino's legacy.
While it is hard to imaging the Red Sox winning it all in 2007 without Beckett, that trade cost the Red Sox 15-20 WAR over half a decade, and set off a chain reaction of decisions that contributed mightily to 3 last place finishes in 4 years. While there is no way of knowing what decisions would have been made, it isn't hard to see how the Red Sox spent a lot of money and traded prospects to recover those 15 to 20 WAR.
In the end, I expect Lucchino's legacy will be as ambiguous as anyone else's, but will still include that he was part of three champion teams.