This psalm ends with the consolation that Yahweh answered their ancestors. He was forgiving to them although he was an avenger of their wrongdoings. Therefore they should extol Yahweh. They should then worship him at his holy mountain where Yahweh, their God is holy.
We see that there are 3 main figures of the past that dominate, Moses, Aaron, and Samuel. Moses and Aaron were called priests. Samuel was more of a prophet intercessor. They cried to Yahweh who answered them in the cloud pillar. Why were these ancient ones of Moses, Aaron, and Samuel successful? They kept the decrees and statutes of Yahweh. These decrees and statutes came directly from Yahweh, so that there was very little dispute about them.
Psalm 99 continues the theme of Yahweh as king. Once again there is no title to this psalm. Yahweh rules as king. The people tremble. He sits enthroned on the angelic cherubim in Zion over all the people. This holy king should be praised because his name is awesome. He is the mighty holy king who loves justice and equity. He has executed justice and righteousness upon the descendants of Jacob. We should extol holy Yahweh as our God when we worship at his footstool. We see the repeated refrain “holy is he.”