Several sites including pocketgamer.fr and WMPowerUser are reporting that King has decided to not bring it's popular Candy Crush Saga game to the Windows Phone ecosystem. (It's "on hold indefinitely".) I suspect Disney and Mojang have much more to do with this than Windows Phone's market share.
Most sites reporting King's changed stance cite poor growth of the Windows Phone ecosystem as the reason for putting Candy Crush for Windows Phone on hold. I don't believe them.
The news, of late, ironically, has been loudly about two things. 1) after a lull while Nokia was absorbed by Microsoft, Windows Phone has significantly improved its market share in the past quarter or so. 2) Microsoft bought Mojang.
The more likely reason: (and I would love for King to prove me wrong, but...) I'm reasonably certain that if King released Candy Crush Saga for Windows Phone right now, it would fail... and I bet they know that.
I speculate that King has been holding their Candy Crush Saga app hostage from the Windows Phone ecosystem for some time, possibly hoping Microsoft would buy King in... a Mojang/Minecraft-like multi-billion dollar play.
Clearly, Microsoft buying Mojang was a smart choice, since Minecraft has almost become a gaming platform of its own. There is a Minecraft community and ecosystem with many vendors producing products and supporting it for their own continued success. I suspect that for those vendors, Microsoft buying Mojang will multiply Minecraft's ecosystem success; the ecosystem will be more broadly and more consistently available to more players.
King, on the other hand, is a one-hit wonder who's core titles are fading as all titles do.
Candy Crush Saga's fading brand isn't the reason the title would fail on Windows Phone, however.
The reason Candy Crush Saga would fail on Windows Phone is because Windows Phone has developed its own ecosystem, and King's niche in that ecosystem has been filled by an even bigger fish... namely Disney.
Yes, Candy Crush Saga would have to compete with the likes of titles such as Frozen Free Fall and Maleficent Free Fall, which are both magnificent implementations of switch/match games that even I have burned some measurable amounts of time and real cash in.
To me, the message is clear. King has made its bed. How embarrassing would it be for King to release it's flagship titles to Windows Phone only to be shrugged off by the Windows Phone app market for the effort? Especially after trying to leverage its brand to strong-arm Windows Phone. Frankly, a failure like that could put King's position in the iPhone and Android ecosystems at risk... which would bring potential value down in the eyes of, say, Apple or Google.
I suspect there are other app publishers facing similar choices. Perhaps they have likewise made their beds. I believe the Windows Unified platform is the platform that successful iPhone and Android publishers can't afford to fail on. Such publishers have two choices 1) get in before a competitor fills their niche, (and succeed), or 2) watch and miss out while realizing in ever more clear hindsight over next decade that Windows Unified was the opportunity they wish they hadn't written off.
[Edit: 1/8/2015 - So King has published Candy Crush Saga to Windows Phone 8, now, and I'm very pleased to see it... it's one less reason for folks to avoid the Windows Phone platform deciding to make the switch or not. Will the Windows Phone edition be successful? By many measures of an app on a platform, it already is. Will it be the success it was on other platforms in reasonable comparison? That remains to be seen, and I still think my analysis is correct, but I think that King still held out for Microsoft to offer up some form of subsidy... I notice that Microsoft has been shelling out for ads for Minecraft, and in those same ad spaces are lots of ads for Candy Crush, as well.]