Why do MEV bots sometimes not include input tokens?

Question

I'm trying to understand some on chain MEV activity and am a bit stumped.

(Edit) Here's the transaction: https://etherscan.io/tx/0x75f0ee27fe3361634e5a051874d877f5e533705cc84ece32529246dc64f2211f

This transaction looks to be an MEV bot making multiple hops between swaps and flash loans. On one of the swaps, log event 202, it makes a Swap on the SushiSwap WETH/FOLD pair at 0xA914a9b9E03b6aF84F9c6bd2e0e8d27D405695Db, but it doesn't send in any WETH, it sends in 5751669306134482050 FOLD and receives back slightly less FOLD 5728662628909944122. Presumably this is just reduced by the transaction fee.

My question is, what is the benefit to the bot of performing this swap if it already has FOLD and is just ending up with less of it?

Is there any better tool for me to analyse this to understand it better?

Thanks

Answer 1

Without really knowing what FOLD is, I can think of a few (dumb, but possible) options:

1. Swapping those tokens gives some other benefits - for example you get to participate in some other action in the same transaction

2. Swapping those tokens makes some token balance be some magic number which you want it to be. Maybe a contract has some logic which does certain things when the number is something. Or maybe there's some weird bug.

3. Maybe things are not as Etherscan shows them. Some tokens may behave in weird ways and explorers may not display things correctly (mostly because the tokens don't do something the ERC20 standard says they should do)

4. Maybe the bot is just dumb and/or has bugs

In the end, it's quite impossible to know what the real reason is. Analyzing this kind of behavior is hard.