There are two important points to the Divine Right of Kings.

Kings received their power from God; and

Kings were answerable only to God.

The second point is subtle, but very important. It meant that the King was answerable to no authority, religious or secular. So, even if a ruler was 'bad', it was no man's place to question this - if God wanted him out, He would do it on His own terms - also called 'death'.

Also, this gave the King Legitimacy. Deposing a king was akin to defying God - and who would be daring enough to follow the damned?