While Fridays are typically the day of the week for politicians to get rid of their political burden, the rule of thumb is to only deliver so much bad news that by Monday it essentially is "old news" already. On the other hand, if a politician goes too far, by Monday the public opinion may be so against them that their political futures may essentially be over. Pardoning Arpaio, and ending DACA on the same day would have given the press a field day, and it would only take a few colorful headlines for this to become a major scandal. After all, Trump just pardoned Arpaio - an individual found legally guilty by an American court.