Complex sentence: At the ceremony, however, Krabs passes him over in favor of Spongebob's coworker, Squidward Tentacles, believing SpongeBob simply isn't mature enough to handle the role.
Split into simpler sentences: At the ceremony, however, Krabs passes him over in favor of Spongebob's coworker, Squidward Tentacles. Krabs tells him that he believes SpongeBob simply isn't mature enough to handle the role.