According to the WSJ yes, MS approached ABK on December to make a first offer. Then ABK tried to find someone else interested to buy it, but ended selling to MS. We have to consider that ABK was in the middle of their huge shitshow in terms of PR and that the development of some important IPs had -supposedly- some important issues and key staff left.
Their current management didn't seem to be able to solve this, so the best option was to sell the company and hope the buyers solve all these issues or at least are convincing to hide it in terms of PR, plus the acquisition would more than compensate what the crontroversies did hurt their stocks.
Its not like WSJ is correct on everything they report. Much like an insider, they are working with information they have heard, not actual facts. So I remain skeptical for several reasons...
One of them being the amount. Even MS being the juggernaught that it is, 70 billion dollars is a shiton of money even for them.So I seriously doubt that all the process I have said(Reaching a consensus, convincing mS top brass of the purchase, convincing Activision and Blizzard top brass of the purchase, checking the legal status of the deal to see if there is a problem, preparing the paperwork, etc) would take only a month, including potential bids that might have slowed it down.
Another is that Activision was in the middle of this shitshow for about a year now. I dont see why in december they felt the urge to speed it up, specially given that Activision was used to being in the middle of a shitshow for more than a decade. So I dont see how they would rush something as important as this, being as powerful as they are.
So yeah, this deal must have been in the works for at least 6 months, well within the current shitshow that Activision was in, and since Sony probably knows everything that happens in the industry(much like any other big company, like Nintendo), it gave them time to react and everything. Having said that, I feel like this all was inevitable after mS bought Bethesda, wether MS decided to eventually buy Activision and Blizzard or not.