Why was sierra game site shut down

Sierra was owned by Vivendi games, which merged with Activision in 2008. It was thereafter closed down, and thus technically no longer exists unless it is sold and later re-opened. Sierra ceased to exist as its own company after being sold originally in 1996: most classic Sierra game fans consider this to be the point in which Sierra's death began, and it gradually ceased to produce the classic adventure games it was known and loved for. It did create a few more (like the much longed-for Quest for Glory V), but those were like death rattles. Future games were produced aplenty, but they strayed far enough from the original companies' style that they might as well have been produced by a random company of some other name.