It appears Gwin never signed a contract, just signed a letter of intent to sign a contact. I'm assuming the intent part is to do with getting all parties of a sponsorship deal in place before actually signing. ie, In order to get a deal with X, he needs to have Y lined up, but can't sign with Y until X is agreed. TWR have signed up a number of team sponsors on the bais that Gwin was riding for them, so TWR are going to have a lot of unhappy folk knocking on their doors ATM and shaking contracts. What a mess.
No doubt we don't have the full story as to why Gwin jumped ship. I'm sure money was a factor, but there has to be more to it IMHO. TWR would have paid up more if Gwin said he was off, surely?