this is just my theory i can be totally delusional.....i think oda was planning for zoro and luffy vs kaido initially. he was supposded to hold off kaido. then he got scared about zoro overshadowing his favorite character luffy and backtracked. thats why oda introduced yamato out of the blue so late in the game to show yamato+luffy vs kaido instead. yamato is unlike other island specific female characters like vivi or rebecca who got introduced early and got huge screentime. even robin got introduced so much early in alabasta because she would eventually join the crew. but yamato is different from them. there was no hint to this character who is suddenly so important and so devoted to oden...... while oda completely forgot about hiyori who is actually oden's daughter and was tied to zoro's character ......the popularity poll was the last straw when zoro almost caught up to luffy.
it doesn't make sense that marco got tired after fighting for half an hour against king when gorosei hyped him up as yonko material. oda did that to force zoro vs king match up.