It's a win-win for both companies in their eyes.
Microsoft can entice the mobile crowd with a popular (read: stuffty knock-off) game they're familiar with and add "includes free games" to the dot points on the back of the box, and King gets the chance to hook more people into their stuffty addiction network so they can get more cocaine money.
Sensible people have been saying they'll uninstall the game, to which I think there will be three possible outcomes:
A) You can just uninstall the game through a link in the start menu or the Add/Remove Programs menu in the Control Panel, or you can disable it in the Windows Features menu.
B) Microsoft attempt to remove all prompts to uninstall the game, but smart(er) users simply delete the files and/or create custom uninstallers so nobody has to suffer with stuffty bloatware.
C) Come launch day, everybody will have forgotten about it, and simply ignore it as they go on check their files transferred successfully and install some games to see if DirectX 12 was worth the hype train tickets.
Nothing major to get upset about. So long as it doesn't shout at me every 20 minutes to play it, it's the least of my concerns as far as Windows 10 goes.