There was a topic where people were asking for any clarification on event conditions and @Juji and @Hime ignored it.
So the only condition to receive event reward was:
Siege: Attack Successful
(Clan Lv. 10+, Character Lv. 85+)
Many people from different clans did not receive any reward, because they were not in PVP zone of their castle by the end of siege. This condition was not mentioned anywhere. @Juji and @Hime we need our reward, we should not pay for your typos/lack of explanation.