It turns out the supply & demand story of economics is basically horseshit, and if you look at how the economy works scientifically - which in this case just means paying attention to what actually happens and letting that shape your theories rather than demanding that your theories are correct and patching them ad-hoc to pretend you were always right - then essentially inflation is caused by price setters just hiking prices.
This is a decent interview with the authors where they also talk about how orthodox economists gatekeep their theories and launder other’s theories so they never have to admit they were wrong: