Sometimes miners can maximize revenue by (counterintuitively) including lower-fee txns.

Maybe those txns paid a fee "out of band" (like Mempool.space Accelerator). Or maybe those txns were involved in some MEV (Miner Extractable Value) scheme.

Additionally, not all miners' mempools are the same. Some mining pools run alternative BTC node implementations like Libre Bitcoin or Bitcoin Knots which have different mempool policies and therefore a miner may exclude a high paying tx that isn't in their mempool.