It is a disciplinary departure that anticipates a promised return.
The staged quality of the departure — gradual, reluctant, moving from threshold to gate to mountain rather than departing all at once — suggests YHWH's careful, deliberate withdrawal rather than sudden abandonment. The radical theological statement of Ezekiel 1, however, is that the kabod appeared in Babylon before the temple fell. YHWH came to the exiles first.
He was present with them at Tel-abib before Jerusalem was destroyed. In the context of ancient Near Eastern religion — where deities were understood as tied to their land and their temple — this was genuinely revolutionary. YHWH is not imprisoned in his temple.
His throne is mobile. His kabod moves wherever he chooses.