Why did President Trump threaten SNL with a federal investigation the morning after a rerun?

Slate

Saturday Night Live re-aired the Dec. 15 Matt Damon-hosted Christmas-themed episode over the weekend, which left many people scratching their heads when the president ranted about the show on Twitter Sunday morning. "Should Federal Election Commission and/or FCC look into this?" the president tweeted. "Usually, this is an easy question to answer," says Matthew Dessem. "Trump gets mad about the cold open, which is almost always so explicitly about Donald Trump that even Donald Trump understands he’s being made fun of. In fact, the cold open of the Matt Damon episode, a riff on It’s a Wonderful Life that doubles as a riff on a famous SNL riff on It’s a Wonderful Life, pissed Trump off enough that he suggested on Twitter that the show was colluding with the Russians when it aired the first time around. If you haven’t seen it recently, it’s easy to understand why Trump would take it personally."