i'm no huge fan of Blair and Brown but there was a global financial crisis. I'm really not convinced that the Tories would have done things differently at the time, do we really think they wouldn't have bailed the banks out?
The finances were going to be in the shit in 2010 no matter who had been in power. And for all his cuts, Gideon's big plan was shit.
The issue is a little more complex than this. The problem was that, to anyone who monitors public expenditure and tax take, Labour, after their first term, consistently overspent above receipts from 2001 onwards during a massive cheap credit boom, and interest payments year on year were reaching £46 billion (over three times the annual budget for the police and justice system at the time). This was a kind of extreme anti-Keynesianism, but was excused by talk of a "new economic paradigm" and constantly referencing climbing GDP (which was itself inflated by cheap money).
It was clear to most watchers that we were living through a false boom caused by cheap credit, and, at some point, that boom would collapse, leaving Britain with liabilities it could not fund through tax receipts.
And that is exactly what happened. After the "global crisis", British tax receipts collapsed by £200 billion. This is the cause of the "austerity" requirement, not that the British state bailed out the banks (those bailouts were largely about the state guaranteeing loans etc) .
Another crippling policy decision was Labour's push for PFI deals to fund capital projects in their first term. They left many public institutions (such as NHS hospitals) with a heavy liability burden that they still have to service out of annual budgets.
A sensible approach would have been for Labour to keep to reasonable spending plans in their second and third term, allowing for the accumulation of a cushion for when the bust inevitably happened. But the problem politically was that Labour had spent years campaigning on the notion that Tory frugality was because they were the nasty party, not because British tax receipts couldn't fund the kind of spend required to fulfil Labour's ideals.
The other interesting point is that Corbyn's economic policies when he became leader were entirely predicated on Osborne either getting rid of the annual deficit through austerity or bringing it down to around £50 billion a year. This is why Labour have been so quiet about Tory austerity; they know they need it if their economic policies are to have any real world viability at all.