1) As stated in the first sentence and the title, he's been arrested in the US which is where he'll face charges and up to 15 years in prison, not the UK. Just because it's reported on a UK website that doesn't mean it happened in the UK. Unlike some US news outlets, the BBC sometimes has a look at what's going on in the rest of the world.
2) What you're doing here is comparing the maximum possible sentence (15 years) with I have no idea what but I suspect specific sentences (possibly time served?) that may have been handed out for the crimes in question without listing any detail that might put that into context.
If the 15 years were a UK sentence the comparison would be that the maximum sentence for rape in the UK is life and the maximum sentence for murder in the UK is life (in both cases meaning 15 - 40 years (Scotland) or 15 - 35 years (the rest of the UK)).
While in reality this may not the the actual sentence or the time served, until we have a conviction and an actual sentence, these are the only valid comparisons we can make.
So, great country? Maybe not, but you make no good argument as to why not.
What else gets you 15 years in the UK? - Repeated rape of same victim over a course of time or rape involving multiple victims : 15 years custody - Rape accompanied by abduction: 11 - 17 years - Murder if aged 18 or over at date of offence: minimum term of 15 years
Right. Leaking data is punishable at the same level as rape and murder. Great country.