By all accounts, convicting grand jury is super easy. They will stamp whatever prosecution wants. But, getting ready for actual court takes time and early arrest don't always matter
Grand juries don't convict. But yes, there's the old "I can indict a ham sandwich" line. Even so, the process still takes time, and even then, you don't get an indictment unless you think you've got a case you can win. What evidence does DOJ have at the moment?