You do, of course, understand that keeping an existing player by awarding a contract extension is great business because there isn't a transfer fee to pay?
Think about it this way; if we'd bought a similar standard of squad player in to replace him for a snip at say £15million then that would be £5 million per annum on the books for 3 years on top of his wages.
Ergo, you'd know that Otamendi's salary was a very reasonable under the circumstances if you had the first inkling of what those circumstances were and had put a bit of consideration in before reaching your peculiar conclusion.
And Otamendi could have got himself a nice big fat signing on fee elsewhere, if he'd chosen to walk at that point, so we obviously had to pay a salary that mitigated that loss (still cheaper than bringing in a similar replacement and he didsn't need to spend a season getting up to speed so it was a no brainer).
Added to that, you must surely realise that the world hadn't been hit by covid and the dreadful financial impact at every level of the game when Otto got his last extension(?) so the current 'force majeur' financial situation couldn't have been a part of anyone's consideration could it?