Originally, Wil directly planned to threaten the Queen with a letter.
In case, if they came to a conclusion that he was the one behind the theft, and branded him as a criminal, Wil already planned to transfer the ownership of Scarlet districts to Aster, and escape to the island of Ormshire.
With 1.6 million gold coins in his pocket, he can develop the island as he wishes, and when he becomes strong, he can return and take revenge.
Then, he thought, negotiating is better than taking such a drastic path. So, he decided to offer a massive amount of gold coins for the Eldershore region.
He purposely offered 500 thousand such that they shouldn't link him to the theft. If he would have offered like a million, then, surely, they would come to a conclusion that he's the thief.
But, seeing their hesitation for such a great offer made a prideful person like Wil, a little bit angry as he isn't even asking to make it an independent kingdom.
