Bail is broken [0], that's the assumption they're starting with. They and many others have observed that bail lends the wealthy an opportunity to walk free with little cost, overfills jails, creates debt/costs for innocent people who are never convicted of crimes and has created a market for businesses to profit off of justice system inefficiency. Whether you agree or not is for another argument. They believe the bail system is not working and that it's a worthy cause to raise money for people that would be stuck behind bars because they can't afford bail.

And while there are clearly engineering costs to mining, this app provides users a passive way to donate to the bail reform cause. The theory is clearly that people who otherwise would not donate will download the app and donate CPU cycles. Getting people to open their wallets is harder than getting people to donate their CPU cycles. "Direct donation is more efficient" is only an effective argument against this if it is the case that every potential user of the app is equally likely to enter their banking information and donate a small sum monthly. I suspect many people who would not be willing to set up a small monthly donation would be willing to donate CPU cycles & electricity.

0. https://www.npr.org/sections/money/2017/07/12/536905881/epis...