You don't honestly expect the tabloids to do ACTUAL sums do you? It's all about emotive headlines.
Quite simply-if the Estate owes the taxman then they've spent the tax that should have been held in reserve to be paid to the Revenue.
They owe it so what's the problem.
Because its the sun. The clear subtext is that 'how dare rich people pay taxes', but they are wrapping it up in a tragic, children with dead mother left penniless angle so the idiots will swallow it.