I'm not at all saying that Austerity was justified by the way, please don't take what I'm saying as any kind of argument for that - as far as I know most economists predicted that it would be counterproductive and they seem to have been right in that despite cutting loads of services and benefits and making life worse for many of those who needed help the most, it did not end up saving any money or reducing the national debt. In fact I would say that Austerity was an ideological act with a made up economic justification.
And I reckon that a lot of the time when politicians say that they are forced to act in a certain way by economic laws they are lying - classic example is Theresa May telling the nurses there "is no magic money tree" when they asked for a pay rise, yet when the election resulted in a hung parliament and the Tories needed to bribe the DUP to form a coalition with them and keep them power, it turned out that, luckily, that thing they'd been growing in the window box and always thought was a tomato plant, was in a fact in magic money tree. Or more cynically they knew had a great big magic money tree but the money that grew on it was only available to use on really important things such as keeping the Tories in power, rather than wasting it on fripperies such as keeping the NHS fully staffed and working.
What I'm saying overall is - still be wary when a politician says that financial constraints force them to enact a given policy, just cos there was one time when the economic constraints did seemingly punish them for enacting a particular policy, it doesn't mean that any time they appeal to that they are telling the truth.