"The LORD is good to all" (145:9). But the same psalm says, "he will destroy all the wicked" (145:20). How do both fit?

Both are in the psalm, and it sets them out without explaining how they fit together. 145:9 goes on, "His tender mercies are over all his works" (145:9). Near the end, the psalm names those the LORD is near to, hears and keeps: "The LORD is near to all those who call on him, to all who call on him in truth" (145:18), "He will fulfill the desire of those who fear him. He also will hear their cry, and will save them" (145:19), and "The LORD preserves all those who love him, but he will destroy all the wicked" (145:20). The psalm doesn't say who the wicked are, and these notes don't name anyone. Psalm 125's notes set 145:9 beside that psalm's prayer, "Do good, LORD, to those who are good" (Psalm 125:4), and Psalm 103's notes set it beside "so great is his loving kindness toward those who fear him" (Psalm 103:11). Each psalm says what it says, and these notes don't set one against another or add to them.