Its a federal crime to manufacture and distribute Marijuana. Its a federal crime to posses certain firearms. Certain states have allowed for legal distribution and growth of marijuana. Why can't certain states pass their own gun laws bypassing federal law the same as the legal marijuana states? Maybe i'm missing something.

You are missing nothing. One is as illegal as the other.

States can pass whatever laws they like.
It won't make those things legal under Federal law.

The feds pick and choose what to enforce, look at the southern border. Obiden was ordered by a judge to reinstate the remain in mexico policy and has yet to do so. They basically do as they please with no repercussions.