I know it's Friday, and others have moved on, but I'll try to answer this as I understand it.
Just read an article about the case on MSN for the first time and trying to understand the crime. The crime would be because he falsified business records to do something illegal. That something illegal would be to win the election illegally. The first is only illegal because of the second and the second is only illegal because of the first. That seems like circular logic and something you can't be guilty for.
No, the first is illegal even without the second, but the second makes it more serious.
The second is illegal even without the first, but wasn't charged independently here.
In 2006 Trump had an affair with Stormy. This may have been immoral, but it wasn’t a crime.
In 2006, Trump did NOT say to Stormy, “I don’t want Melania to find out about this, so how about we keep this quiet and here’s $130,000 to help you have a nice life”. If he had done that, it would not have been a crime.
In 2016, Trump and Michael Cohen conspired to engage in election campaign fraud, trying to illegally influence an election. That IS a crime, but it’s not the crime that he was charged with. I’ll come back to this in a bit.
In 2016 and 2017, Trump created false business records, when he paid money to Michael Cohen and wrongly recorded that they were legal expenses. “Falsifying business records” is a crime, but a low level one – a misdemeanor. This is not the crime he was charged with. As others have noted, many misdemeanors are never prosecuted.
What Trump was charged with was “Falsifying business records with the intent to commit or cover up a crime”. This is more serious – a felony – and this is the only thing he was charged with. (34 records were falsified, so he was charged 34 times, but it was all part of the same crime.) The crime he was trying to commit or cover up was the crime of violating election campaign laws.
To conclude that he was guilty, the jury had to agree unanimously that he had falsified business records, and they had to agree unanimously that he did so with the intent to violate election campaign law. They were unanimous, and he was found guilty.
There are many ways to violate election laws, and Trump himself has long raged against such violations: votes from dead people, miscounting votes, etc. Trump’s own violations were with regard to campaign finance law, and included at least three separate violations which were alluded to. He conspired to pay $130,000 to Stormy with the intent to influence his campaign, so this is considered a campaign contribution and, like the cost of his rallies and ads, he was required to report it to the Federal Election Commission. Instead, he had Cohen pay Stormy, and then fraudulently had his repayment to Cohen be recorded as a legal fee, such that Cohen owed tax on this fake “income”. So there were false reports to the offices of state and federal taxes.
If Trump had been charged here with violating election laws, then the prosecutors would have called witnesses and submitted evidence regarding exactly how he committed that crime. They did, in fact, do this when charging Trump’s co-conspirator, Michael Cohen, for his part in this same crime. Cohen was convicted and spent several years in jail for making an excessive campaign contribution ($130,000 to Stormy) for the purpose of influencing an election. Cohen admitted that he had done this at Trump’s request, and so it would not be surprising if Trump were also charged with his part in that crime, but he wasn't.
Since the current charge was “Falsifying business records with the intent to commit or cover up the crime of campaign fraud” the jury was only provided with the evidence for that charge and not given all the details they'd need to determine his guilt in “excessive unreported campaign contributions". So the judge told them that they did not need to reach consensus about the details of that campaign violation, but simply agree that some campaign violation had occurred. One juror might think he made an excessive unreported campaign contribution, while others might think he also had evaded paying federal or state taxes. Even if they disagreed about those details, their decision would be considered unanimous for the charge of “Falsifying business records with the intent to commit or cover up a crime of campaign fraud” if they were unanimous in finding that some campaign crime had been committed.