Paying out the whistleblower before the victims would be like if someone stole your bike, then the cops arrest the guy and recover your bike because of a tip... and then the cops give your bike to the guy who called in the tip
The crime has already been committed. The whistleblower is the reason you're getting anything back.
...and then figuring you could get victims 100% of their losses back by taking that 10% from the whistleblowers and sending them to the back of the line, and then coming back a year later and seeing that...
...while victims were getting 100% of their losses back when these crimes were discovered, very few of these crimes were being discovered, and using your impeccable logic concluding that the crime rate must have gone down! who needs whistleblowers!?
We do not have a justice system in which the victim pays for the cost of investigating, prosecuting, and punishing offenders. All of that is paid by the general public. That does not mean there are no bounties -- there are, but the bounties are never paid by subtracting out amounts due victims. Changing that, so that victims would not be entitled to full restitution in order to help finance law enforcement would require changing a lot of laws, not just adding a whistleblower law. It would also overturn a lot of precedent. It would be a big change that a large majority of the public would oppose.
source?