TL;DR: economists are still stuck in the idea of the market as a perfect force for reaching optimal outcomes. They're ignoring the simple fact that businesses are putting prices up purely to increase profits. And that they can do this because the economic ideal of perfect competition (where many small firms compete with near-identical products) does not exist. We have a small number of very powerful businesses—oligopolies—in nearly every market for consumer-facing goods.
The inflation is, quite simply, because we've been printing money since the early 2000's, and the shit hits the fan eventually. Every time any company fails due to massive corruption, it's bought out with printed money. ..that, and, the covid "please don't riot" checks. Fiscal irresponsibility and corruption, plain and simple.
Free market capitalism is a myth - capitalism doesn't work without a separation of corporate and government interests, and in free market capitalism, the government gets bought.