This looks like a "sandwich" (aka front running) attack executed in the same block
How come "pre" and "post" transactions have 0 fee yet they appear at the very top of the block and right around the "victim" tx? Is it the miner creating those transactions themselves?
The miner was paid directly, rather than through gas fees, by an attacker wanting to front-run the victim's trade.
If you look at the "post" transaction, specifically at the internal transactions, you'll see there was a transfer of 0.129472988593493943 ETH directly to the miner's address.
This is only paid on the post transaction, therefore incentivising the miner to construct the pre-vitim-post bundle, in that specific order.
To bring all this about, the attack - via this contract - involves a
block.coinbase.transfer(<amount>) call. (When the block is mined,
block.coinbase is set to the miner's address.)
Miners can watch the mempool† for transactions offering to pay them directly, and will then construct the sandwiches if the direct fees are sufficient.
For more information on Miner-Extractable Value (MEV), see:
†While miners can watch the mempool for transactions that pay them directly, in this specific case, that didn't happen.
If you look at the top of the page for any of the transactions in the bundle, you'll see a purple "Private Transaction" label, below the page title. This means that Etherscan didn't see the transaction being broadcast to the public mempool, which means the attacker was either a) the miner themselves, or b) someone with access to the miner's dark pool. (A dark pool is a private/permissioned mempool that users pay to get access to. See: Escaping the Dark Forest)