AC - Apple Cultist
It's maybe more likely that many people held off buying a tablet until they were higher-powered (as they are now) and that such a demographic of people, being more circumspect and probably thrifty couldn't see the point in spaffing a wedge more cash on an iThing when a droidThing does the same and cheaper, lighter, waterproofier (in the case of stuff like the Z2, at least).
Chances are they already have a droidPhone too (statistically) so logically a tablet would also be a droid so they could have familiar apps. Then they start using the internet on it as a tab is way more handy for webbyness than a phone.
So the stats increase.