It was awful and I still don't understand what goes through a person's brain when they deliberately set fire to something, but esp something where innocent lives will no doubt be lost, be it human or animal.
But the generosity of the public has been overwhelming - close onto £1.5million raised (if not even more by now - I haven't looked) and so many places (such as Pets at Home from the link you posted Aggers) doing their bit as well. At one point I gather the police had to ask the Manchester Dogs Home to put a note onto their FB page to ask people bringing donations to go to other places as the motorways and roads heading towards them were jam packed and the traffic was at a standstill.
It's sad that it took such a horrid event to get people to donate / adopt a dog - but still; at least people world wide really rallied round.