There are various explanations based on situation.
Throw some examples (token and exchange) and i'll explain it from economic point of view.
is that money laundring?
It might be. But it needs to be backed by volume from nowhere. If 1000$ was used to make pump (what is common on low volume coins on dex's) than it's definitely not money laundering.
Could you pls explain mdab/bnb trading? here is the link ;
https://www.binance.org/en/trade/MDAB-D42_BNB2 days in a row, this is just an example there are many tokens like that at various exchanges.