It’s harder to understand the sentencing from that link because the Daily Mirror have reported it as 2 years for murder, and then further down the article that he was convicted of manslaughter
All sentencing is on a scale, and for manslaughter it is between 1 and 24 years of custody.
https://www.sentencingcouncil.org.uk/offences/crown-court/item/unlawful-act-manslaughter/
Culpability in manslaughter of A-C have an intent to cause harm, and the sentence is 2 years which indicates the court did not find that level of intent, and 2 years is the starting point.
Then any aggravating and/or mitigating factors can increase or decrease the sentence. The final sentence remained at 2 years so either there was no change or both aggravating and mitigating factors balanced each other out