In the case of the US, money is initially created through the FED. The government sells bonds to the FED, the money to pay for it is created to do so, it does not exist beforehand.

The much wider issue that propels the inflation forward are actually the retail banks, not that they are necessarily to blame, they of course operate within the parameters they are allowed to.
Here's an example:

You pay company X $1mil to build a house in cash.
X deposits that money into bank A to pay its employers. 10% of the cash is held as reserve, the rest is loaned out.
A worker recieves money and deposits it into bank B, with his wage he buys a new TV. 10% of the cash is held as reserve, the rest is loaned out.
The TV vendor deposits his revenue in bank C, and pays his employers from there. 10% of the cash is held as reserve, the rest is loaned out.
The employee of the TV vendor spends part of his wage on buying new shoes and deposits the rest into bank D. 10% of the cash is held as reserve, the rest is loaned out.
And so on.

Retail banks are extending the money pool, that was created out of thin air to begin with, even more every time money is deposited and then loaned out.

Everybody loves the cheap, infinite money.
Banks love it because they can loan out much more money than they could if they actually would have to hold 100% reserves.
Businesses love it because it allows them to expand at greater scale.
Private persons love it because they can afford things in the here and now instead of having to save up for it.

Everybody loves fiat money until the next bust is in.