I'm pretty sure greed is usually the cause of inflation.
Nope, but that's what the politicians want you to believe! Inflation is really an increase in the money supply per unit of economic activity. Roughly like (MoneySupply/EconomicActivityLevel). The most common cause to drive that equation positive, meaning INflation (though not the only possible one), is wildly adding too many new dollars when the underlying economic activity does not also rise accordingly. This means all dollars in circulation are each worth less.
Please note I'm not saying increasing the money supply is bad. If the economy actually grows, it makes sense to "print more dollars" if your goal is to keep each dollar worth the same effective purchasing power.
However, that is NOT what is happening. What we're seeing today is the end game of decades of irresponsible government behavior. First the huge bailouts of the 2007-2009 era (the "Great Recession") where economic activity was flat or declining, yet gobs of new dollars were tossed into the market for political reasons. No politician wanted to fall on his sword to vacuum those dollars back out of the economy later, so the ratio began to swing... but the politicians also pressured the Fed to keep interest rates ridiculously low to artificially prop up the economy rather than let market forces naturally absorb those new dollars and have inflation gently accommodate them over a period of time.
This has continued until COVID-19, the straw that broke the camel's back. Once again, economic activity dropped yet they responded by throwing record amounts of unbacked dollars into the economy. There are delays in the system, so the sugar high felt great for a short time, but all that pressure has been building... and now instead of graceful accommodation over long periods of time, the natural laws of economics are reasserting themselves. The money-printing binge of yesterday becomes the pimple you pop, the mirror you clean, tomorrow.
The imbalance has become too great. The Fed cannot keep rates close to zero any more. And again, no politician is willing to sacrifice their career to do the correct thing and suggest pulling those dollars back out so the ratio of dollars to economic activity is roughly at parity again. Greed - at least economic greed by companies, which is what I believe you were implying (if I'm wrong, I apologize but I hear this from a lot of people lately) - is not the cause of inflation and corporations have no way to influence the money supply. If someone thinks they can "just raise prices to gouge people" someone else in the market will be glad to steal their customers. Except that isn't happening because the corporations are stuck in the same situation as everyone else. Their costs are rising too. Generally speaking nobody can radically undercut the other guy's "robber baron pricing" because that pricing is driven by actual cost increases.
I'm sure there are some edge cases out there. But this is reality for the vast majority. And it all comes down to too many dollars for the level of economic activity. Hey, if you WANT to devalue your currency, have at it. Venezuela offers the most recent example but they're far from the first and won't be the last. But if you want responsible economic policy, you seek to avoid wild gyrations like this by allowing normal market forces to see cyclic ups and downs along the way, none of which are so extreme that they end up being given historic names with leading capital letters. When this happens, it's a failure of your politicians, period.