I guess it'll have something to do with him showing genuine remorse and not being a bad person, just a stupid boy making a very stupid and costly mistake. In the end, it's up to the legal system to balance the severity and malice of the offence against how much of a valuable member of society he could be in 10 years with a bit of prison time and discipline. It's emotional because those three young lads are never coming back, but I guess the law exists to take emotion out of it - as cruel as that sounds.
I was down in Faringdon and Abingdon recently for a friend's 25th wedding anniversary, nearby to where this crash happened. Those country roads between Swindon and Oxford are unexpectedly dangerous at night - they're wide open and there are long, long stretches with no traffic lights in places. Sadly, it's easy to see how a bunch of lads doing NOS on a weekend could get giddy and egg the driver on a bit to try and "top a ton" as the game goes. It's no excuse, it's just probably what happened, and I guess it all gets taken into consideration.
A similar thing happened in Cheadle in 2016, if anyone remembers? A lad from my old school - Declan Blackburne his name was - got killed in a police chase. He was the passenger of a car that was speeding along Bird Hall Lane in Stockport at about 3am. The police spotted the car and chased it - the car hit 70mph on Councillor Lane, hit that S-bend outside the Spar, and careened straight through a lampost and into a tree. The driver literally ran away from the scene without a scratch while Declan was trapped in the car and died two weeks later.
The driver had traces of cocaine and cannabis in his system when he turned himself in the next morning. He got given six years but only served three, from memory. He got time off his sentence in the end because he was genuinely remorseful (in the judge's eyes) and had turned himself in. Three years behind bars for something like that is never gonna feel like enough but I guess there's just a precedent and a consensus that's been developed over time. Declan's never coming back and neither are these lads, though.