The country has a different approach to internet content than the US, and typically bans sites that revolve around child abuse and exploitation. There's no mention of the ISPs blocking sites under that law, but Vodafone argued that it was the "responsible" thing to do. The shooter posted his video with the intention of spreading hate and stoking social tensions, and the ISPs don't want to play a role in either.

It's not clear that this will be effective. It's trivial for many people to change their DNS settings, use VPNs or otherwise dodge around virtual barricades. It's also bound to raise cries of censorship from critics who believe that videos should stay online if they aren't explicitly illegal. However, it's safe to say ISPs aren't particularly concerned about either point -- they'd rather take some action than be accused of exacerbating an already terrible tragedy.