since secretaries of state violated the law by c hanging election rules that ONLY legislators can do shouldn't the election be redone?

The state constitution,  passed by state legislators, gave thempermission..

Since state legislators wrote the Constitution/Amendments how was the law violated?

Actually by the legislators  writing the State Constitution THEY DID NOT CHAHANGE THE US CONSTITUTION.  They followed by giving the secretary of state the authority 

Thats why the State courts ruled the way they did

The "Trump LOST"  Hotline has operators standing by 24/7, to help talk you down off the ledge.

The election was held.    TRUMP LOST- 

Challenges were made, like the ones you claim here.   JUDGES, some appointed by TRUMP.  disagreed with you. 

Challenges of Fraud were made in court, over 60 times. 

You LOST all 60 of those challenges,   again,  some presided over by Judges appointed by TRUMP. 

Mainly because they failed to provide a shred of evidence for their claims. 

At this point..........you can kick and scream and wail  and tear your hair out all you want........TRUMP LOST..........and Biden is the president. 

Why did every Trump appointed Judge who looked at those accusations disagree with you? 

Nice theory, but not the one adopted by the U.S. Supreme Court.  

The Supreme Court held about eight years ago in a case involving the equivalent clause in Article I that "legislature" referred to the legislative power.  (As a matter of historical reality, it would have to refer to the legislative power.  At the time of the framing, the thirteen states had thirteen different sets of rules for what it took to validly enact a law.)  

Furthermore, in most, if not all states, the legislature has delegated its power (which is constitutionally permissible) to the Secretary of State to make regulations implementing the statutes. As such, the legislature has approved allowing the Secretary of State to change those regulations as long as the revised regulations are consistent with the statute.  And it's up to the state courts -- not the legislature -- to decide if regulations are consistent with statutes.

Similarly, because we are dealing with the legislative power, it is up to the courts to reconcile different laws passed under the legislative power which would include the legislative power of the people of the state to adopt and amend a state constitution.  

the Constitution has no provision allowing that

My opinion - no.

Judges felt otherwise.  And there is no mechanism to "redo" a election, especially if it's only because you don't like the result.