Some Questions on Champs and Strats

So recently I've been watching the LCS and had some questions, in case there's something I'm missing.

1. Why has Lucian come back into meta? Why pick Lucian over Graves?
2. Why pick Ezreal over Corki?
3. Why pick Ezreal ADC over Ezreal Mid?
4. Why pick cleanse over heal?
5. Why pick barrier over heal?
6. Why has Diana made such a comeback?
7. Why has Viktor made such a comeback?
8. Is Lissandra a mid or top laner now?
9. WHY ISNT HUEDEKAISER META (Don't answer this it will make me sad)
10. Why is Veigar support becoming a thing?