Why is it important to reject the omnibus ANOVA null hypothesis before performing Tukey-Kramer tests?

Because Tukey-Kramer is a post hoc follow-up that assumes evidence that not all group means are equal, and it is intended to identify which specific pairs differ after that omnibus conclusion.

Because performing Tukey-Kramer before ANOVA always inflates Type II error and is thus prohibited by statistical rules regardless of design.

Because the Tukey-Kramer test relies on pooled medians from ANOVA which are only available after failing to reject the omnibus null hypothesis.

Because Tukey-Kramer requires the overall F-statistic to be less than alpha to ensure that pairwise variances are homogeneous across groups before pairwise testing is valid.