Trump didn't win because he personally had social media accounts from which he spread his message - canvassing by his followers (until they kept going Nazi and getting banned) were what was effective. Trump's own social media use has been a net negative for him, he mostly just rants and shitposts. If he'd been banned from Twitter earlier, he might have gotten more accomplished.

Also, coverage of Trump by the mainstream media was likely far more effective than social media at getting him elected. If nothing else, it provided the material that got spread across social media.

Obama's victory was due in large part to social media as well, but not due to Obama's personal accounts.