Is this a way for Big Guy to launder money?
Exactly. This is what they do to show payments as loans.
This is what the notes on the checks to Biden's brother kept using- Loan Repayment.
That seems the most likely answer. Most of these seem to be lines of credit (HELOC), where he was borrowing large sums of money and almost immediately paying it back. Had anyone else done this, it would have attracted the attention of the IRS, FBI, etc.
There is absolutely no way of telling how much Joe and his counterparts in Washington & elsewhere have squirreled away unreported and off-shore. I’ll bet the intelligence services know, and use it to coerce certain actions from the crooks. Money corrupts everything it touches, and the bigger the money the greater the degree of corruption.