This is what I've been able to piece together as the Blizzard lineage from its founding. Care was taken to put events into context, and to describe what these companies were doing when they existed and why mergers happened. These ancient texts may not be perfect, but they were kept in a series of clay jars in the desert for many years.
Silicon & Synapse was founded as a small indie gaming company by 3 UCLA graduates on February 8th 1991: Mike Morhaime, Allen Adham and Frank Pearce ( I believe he was also Batman but I'm not really sure). They changed names to Chaos Studios in 1993. Their goal was to get huge. They didn't have the expertise on how to do that, and the most efficient way to achieve the goal was to just get bought out by a big company who could provide the expertise. They wound up getting bought by a company called Davidson & Associates in 1994, just before the release of Warcraft I later that year. Davidson & Associates claim to fame was the Math Blaster educational video game (and its associated empire of Blaster video game titles). The original Math Blaster came out for the Apple II WAAAAY back in 1983, which is about when D&A was founded. D&A changed the name to Blizzard Entertainment because they refused to pay the fee to the owners of the name Chaos Studios.
But D&A wasn't long for this world. D&A (and Sierra On-line) was bought in 1996 by CUC International. CUC international was a sort of pesudo-Amazon in the mid to late 20th century. They offered a variety of products and services as a middle man. You ordered from their telephone service and they shipped directly to you. While the Sears catalog operated mostly as a physical book of massive size, CUC International was telephone and online based and offered personal services like travel, dining and financial services like a concierge service. Maybe think of CUC International as a cross between Amazon and Travelocity. In the 1990s, CUC International offered online shopping services on AOL, Compuserve, Prodigy, Genie, and Delphi.
CUC International was basically destroyed in 1998 by what was then the largest accounting scandal in corporate history. CUC International was effectively nuked off the planet by prosecutors. The remnants of the unethical company (CUC International) was merged with an ethical company (HFS or Hospitality Franchise Services) to clean up its image. This new company took on the name Cendant Software (of which Blizzard was a division of). Of historical note, Jeff Bezos takes Amazon public in 1997 at the PERFECT time and Amazon fills the galactic-sized crater in online retailing left by CUC in 1998. Amazon comes out of nowhere from a nothing company to a huge retailer as they just naturally expand to take over where CUC once dominated. Then to further clean up the image, Cendant gets sold to another company called Havas in 1998. And then to FURTHER clean up the image, Havas merged with a freaking utility company in europe called Vivendi. Vivendi is an interesting story in itself as it originally was founded as the public water company in France around the time of Napoleon. Over time, they morphed and became a tech company. Really weird.
In 2006, Bobby Kotick, CEO of Activision since 1991, wanted to get control of World of Warcraft and gain a strong foothold in the Chinese market. He proposed a merger between Activision and Vivendi games. A deal was struck, and Activision-Blizzard was formed. The new company was a subsidiary of Vivendi because Vivendi owned a majority stake of the shares of the company.
From 2008-2013, Kotick, Morhaime and the boys were all employees of Vivendi.
In 2013, Activision Blizzard bought itself out. Vivendi sold all of its shares in the company, dropping from majority shareholder to completely exiting the company altogether. Activision Blizzard paid about $5.8 billion to do this.
And that is where the company sits today.
Sources:
https://en.wikipedia.org/wiki/Blizzard_Entertainment
https://en.wikipedia.org/wiki/Davidson_%26_Associates
https://en.wikipedia.org/wiki/CUC_International
https://en.wikipedia.org/wiki/CompuServe
https://en.wikipedia.org/wiki/Blaster_Learning_System
https://en.wikipedia.org/wiki/Amazon_(company)
https://en.wikipedia.org/wiki/Activision_Blizzard