The Bibles have nothing to do with his campaign. In the context of the Bibles, he's just a dude selling bibles, he's not a representative of his campaign, the money isn't going to his campaign, and it's not being spent on his campaign.
To be specific, there's no law against a church giving money to a political figure; there are laws against donations to political causes -- and political campaigns are political causes. Trump the person can sell whatever he wants and use that money however he wants, or, in this case, license his name to whatever, etc.
There's no reason a person can't pay for their own campaign, and there's no reason someone with more money than sense can't just give another person free money with no strings. We don't tend to this because we don't tend to have candidates that could believably get money from people for reasons unrelated to their campaign -- with any career politician, it would be a transparent pretense. But not with Trump, he legitimately can get people to buy whatever, because it's him they like, not just him-as-president. The shoes, the Bible, the steaks -- they're proof of that fact.
The money he's getting from the Bibles is not political money and he's not spending it on his campaign. There's just no there there.
Trump's debts are not "political," especially the fraud verdict (the $400m one) which is his biggest problem rn. There's no reason a person can't sell a Bible and use it to pay for the judgement against him for fraud. Like, that's a weird sentence, but it's true.
His campaign is definitely short on money, but, financially, his main concern right now is the fraud judgement, and after that the rape/defamation judgement, then maybe the lawyers next? Tho he probably doesn't plan on paying them. So, yeah, Trump's going to need some money for his campaign, but he needs to keep the Trump in Trump Tower or he's completely fucked -- legally, financially, and even politically.
Look, I hate him too, but this is just not money laundering.