Because it was the Tory party who turned off the taps in the first place? The Tory party that has been in charge for most of the time of the last 40 years? Because populism is a fraud of promising easy scapegoats to point fingers to and avoid hard questions? For example just a few weeks ago a coalition of opposition parties supported a motion to increase substantially investment towards young people (free school meals, school supplies, catch up resources for teachers/students, extracurricular activities, mental and physical well being etc). It was put forward after the government rejected the funding proposals put forward by an outside commissioner and instead made a proposal that in comparison is peanuts. Not a single tory bothered to vote on the motion sticking by the party line. Similarly when it comes to voting records on public investment this "populist" party still looks very Thatcherite whereas "centrist neoliberal" labour have been the ones backing the proposals as the minority party. It's the easiest thing in the world to adopt populist soundbites but examine the voting records and the tories do not match their words.
So I don't necessarily disagree with your attribution of blame, but I think that attribution is mostly meaningless in today's political landscape.
For whatever reason (Starmer/Corbyn's inability to pin Johnson down, a supine media class being happy to act as Tory party propagandists etc), I don't think your average voter in say Sunderland or Hartlepool associates Johnson with the Tory party decade of austerity.
They've seen 40 years of steady decline under Thatcher, Blair and the coalition government so don't believe that any party has the will or the ability to improve their lives and restore their communities. They've also seen the very explicit offer of Johnson's authoritarian populism, which to some extent he's delivered on (or at least the facade of). I have canvassed for Labour in the last 2 elections and one of the most common responses in deprived areas in 'the red wall' was agreement with Corbyn's policy proposals but utter disbelief that they would actually deliver them. "I voted for Brexit 4 years ago and the politicians still haven't delivered that, why should any other policy be any different?".
What they've seen of Johnson is 'getting Brexit done' and what they've seen from their new Tory MPs and mayors is local people who have been able to persuade Westminster and the Treasury to turn the taps back on for regional investment. Of course most voters know it's cynical pork barrel politics, but why should they care? In their minds the choice is between the party they associate with their moribund council who has presided over the death of their community for the last 40 years (and a central party that they see as too liberal, metropolitan and out of touch) or a cynical bunch of poshos who may at least be prepared to bribe them into supporting them.
A good example for the above is the new Tory Mayor of Teesside. He's nationalised the local airport, removed parking charges at the local hospital and started a development corporation to supposedly bring industry back to the old steelworks and ports. Voters of Hartlepool think of him when they consider voting Tory, not Thatcher or Cameron.
Factors you mentioned like the motion for education funding (which I presume was an early day motion?) don't cut through to anyone not paying attention to politics, which is becoming an increasing number of people since they've lost any faith that politics as performed in Westminster will improve their lives. That attitude of course benefits the Conservatives and raises the barrier for any progressive party to persuade the public they will deliver. Especially when the current Labour party can't support a decent pay rise for nurses, opposed an increase in corporation tax and abstained on any remotely controversial bills like spy cops and overseas operations, so the public are rightly querying what the hell they actually stand for. I agree that Labour would be better for our NHS and public services, but the more progressive, concrete and popular policies of Corbyn weren't sufficient, so I don't see any evidence to think that being more progressive than the Tories on public services will get Starmer anywhere.
If you add to that the cultural signifiers which have become increasingly important as politics has moved away from anything material then it's a mix that I think is far too heady to be challenged by Starmer's woke 'competent' centrism.
The TLDR is that to if you're a homeowning white guy in the 'red wall', there's a triple lock on your pension and your home has increased in value. It's going to take a fairly convincing proposal to make you want to return to a party that currently represents very little of substance, aside from the sort of liberal identity politics you associate with the metropolitan liberalism that often forgets you exist.
If you're economically marginalised, then I don't see why you're going to vote for the bloke who isn't proposing anything to radically address your issues.
Hence why I think his appeal will be limited to liberal centrist dads who think Johnson is a bit too rude and racist for their tastes. And they don't win elections without the North and Scotland.