It is a huge amount of luck. The biggest correlation to giving up runs is letting guys on base and right now Hader is doing that a lot. He's stranded 93% of runners he's given up this year, that should be expected to be about 75% going forward. He's given up a .211 BABIP against RHB's and .236 overall that is unsustainable, it will regress towards .300 going forward (everyone besides huge GB pitchers do) He's also faced way more LHB's than he would as a starter thus far (40% vs LHB's). His xFIP is 5.03. I'm rooting for the guy, and want him to be a great starter, but thus far, every single peripheral he has shows he's been put in the best possible position to succeed (good on CC for that) and he's been lucky.