They weren't, millions were still watching BBC 1 and ITV, albeit in reduced numbers.
Yup, millions watched the funeral (13mill I think I heard? If so, that's more than Line of Duty! ). The royal-haters should really take that on board, as no-one was made to watch it.
The problem was the 2-3 days following Phil's death. Did 13 million watch any of the news programs when he was 2 days dead? Did cancelling the BBC2 schedule help anyone through their grief?
In general I think your direct numeric comparison is flawed anyway; the BBC could show the most appaling things - live executions, child porn, you name it - and they would get 500 viewers for every person that bothered to complain.