"it is said that a long string of small metal circles
welded together by a blacksmith is more likely to
be pulled apart if one of the small metal circles is
not as strong as the rest of the small metal
circles
"a chain is only as strong as its weakest link"
why is the shorter version more effective?
it makes the idea clearer
it is more concise
it is more easily understood
it creates a stronger image

An inference that can be made is that the princess is bothered about the tiger door. although there are reasons for both this one has a better reason. the princess is not a monster and even if she didn't want to marry this man she wouldn't want him to die. the grudge of death is pretty heavy. unless she has done this before and feels no regret then she wouldn't want to be married to someone of low quality, if he is low quality.