There's been evidence that the Trump campaign did a massively better job of taking advantage of Facebook than any other campaign, Republican or Democrat, had previously.

There's also evidence that Facebook's advertising models were a massive help -- the Trump campaign and affiliated organizations were paying much lower advertising rates than the Clinton campaign + affiliates, largely because Facebook's model prioritized the kind of controversy-and-outrage-generating stuff Trump was putting out there (since controversy and outrage drive engagement, and engagement is the metric Facebook cares about).