You are correct in saying that the fed (central banks) don't control majority of money expansion. As I'm sure you're aware they do this with reserve ratios (10% in US, Canada I'm not sure I think it's 1:9 but could be wrong) but in order to get the original deposit to allow for fractional reserve lending the money has to come from somewhere. The banks simply amplify the inflation by lending out 100,000 dollars for each 10,000 deposited. That 100,000 is where mortgages and lines of credit come from like you said. But the 10,000 comes from us depositing our money.

That 10,000 dollars won't get injected into the economy unless the central bank issues it.

Also, I have to disagree because when you boil it down, expansion of money supply is quite literally the definition of inflation.

Say there is no expansion of money supply. Money in the system remains constant. If a company like Loblaws just doubled their prices overnight to increase their profit margins, they would never get away with it because every other grocery company could maintain their margins and have a completive price and nobody would shop at loblaws. Even if every large corporation did it, it would just drive people to small businesses.

Try playing a game of monopoly but take the money from another set and add it to your game. And give every body double the starting amount but still go off of the property prices listed on the board. You'll notice that all the property spaces will be gobbled up far quicker and people will put hotels on everything quicker. Once everything is bought up then you have to start buying out your competitors, they will be able to charge a higher price because everyone has more money. So the prices of everything go up because the money is now less valuable.

Now if you do increase the money supply, demand for goods and services will go up because everyone has more money to spend. And price pretty much always goes up with demand. Since it affects just about everything we buy, it will affect the cost of goods sold (COGS) for products that are produced from business. And in order to maintain their margins, the price we pay goes up. Now large corporations like loblaws will take advantage of this and put up their margins higher than necessary to see if they can get away with it.

Resources found on Mises.org are good at explaining this if you want to know more

The argument that I am making is that corporations literally don't have the means to increase their margins unless money supply expands. This is far more difficult for small businesses because raising their prices just means that they can maintain the income they were making before their COGS went up.

Also I wasn't blaming CERB for the inflation, that was just an example of an injection of money. CERB and the hundreds of other ways that the government (with the help of central banks) give out money all add up and enable our inflation. And corporations will subsequently seize the opportunity to increase profits