I would tend to agree that this is the weakest case and the sentencing is likely to reflect that, but your post muddies the waters of what he is actually being accused of here which is far more mendacious than is being made out.
Nobody cares that he fucked a porn star and paid her off (except maybe his wife). That isn’t illegal. Ethically questionable yes, illegal no.
What he’s being charged with is knowingly fudging his business accounts with the ultimate aim of violating campaign financing laws - and not just violating them in a technical sense, but in a big way. And there’s some really important context needed here. The maximum any person can donate to a political candidate for federal office is a few thousand dollars. Businesses are expressly prohibited from making donations directly to political campaigns. They can donate via a PAC which is a fund that is set up to collate money from larger donors but importantly is also regulated and forbidden from coordinating with individual campaigns. This is to prevent businesses from colluding with political candidates for president and bribing them with undue influence.
What Trump has effectively done is take $130k out of Cohen’s coffers and $150k from AMI (the company that paid for the McDougal story) and donated it to his own campaign without declaring it - that’s over 100 times the legal limit on donations, and includes a payment taken from a business. That is very illegal, it impacts things like tax calculations, but also contravenes a fundamental principle of the US political campaigning system. He can’t just create an unlimited piggy bank for his political campaign by letting anybody pay for hundreds of thousands of dollars of costs, and he can’t take those donations from AMI either, that isn’t at all how it works.
We can argue the toss about how much of an impact that actually had on the outcome of the election. I agree, probably very little, and I also agree it’s not a “satisfying” charge to find him guilty of. It’s basically in the same domain as Al Capone getting done on tax code violations. But Cohen went to prison for these things and if we donated £280k to Biden’s campaign tomorrow and fudged our accounts to hide it, then we would go to prison too, because it is fundamentally about undermining the democratic election system.