What does "blocked provisionally" mean? Could it mean that CMA would allow Murdoch to buy the rest of Sky and own all of it, provided he then sells the whole of Sky to Disney? It's a bit like a buyer paying the vendor of a leasehold property to buy that property from the freeholder/landlord, whereupon the buyer is then able to buy the vendor's property which is now freehold. That kind of deal (either to freehold or to extend a lease) is quite normal and lawyers can make it a binding contract between vendor and buyer, conditional on the lease being extended or enfranchised into freehold. In this case the binding contract is between the vendor (Murdoch), the owner(s) of the remaining Sky shares and the buyer (Disney). All money, offered shares and signed contracts would be held in escrow by the lawyers until the British government followed through on its undertaking to allow the sale and change of ownership. Getting the Government's "promise" is not enough, as Paul Reichmann found out to his cost when Margaret Thatcher did not keep her promise to provide transport infrastructure if he proceeded with Canary Wharf - for the first few years what he built ended up as an un-sellable no-man's land - one can easily imagine how much flakier and untrustworthy any such undertaking would be under the dead sleight-of-hand of Theresa May).
I think Disney's reason for acquiring Sky would be fivefold:
1) it's a prestigious asset.
2) it's a nice earner
3) Disney's ownership image and track-record would be less of a liability than Murdoch's when politicians start bitching about media plurality versus monopoly
4) Sky is already big across Europe and that might serve Disney's ambitions
5) Disney's intention to operate a streaming service to compete with Netflix could be within the aegis and resource of Sky. In the short-to-medium term, Sky-Disney would be catering to two markets (Sky-Plus as it is right now and Sky-Plus with streaming. Better to allow a degree of self-cannibalisation between these two Sky-Disney businesses than have a competitive streaming company do the devouring.