In the incredibly unlikely scenario that two individual miners both chose all the same transactions in the same order, and generated the same Coinbase transaction sending the same coins to the same address, and used the same timestamp, and started at the same nonce, and so on, then they would simply duplicate the work needed to mine that block.
Incredibly unlikely? It's impossible, unless,
1. There's mining software with feature deterministic/reproducible mining.
2. Multiple party using same mining software with exactly same parameter (e.g. address on coinbase transaction).
3. Both party's node receive have exactly same transaction set on mempool before creating block template.