All eyes are on the BNB due to the increase in Ethereum's gas fee. Thinking about the beginning, it can be understood that the BNB's gas free is increasing day by day. Although I don't know the exact reason behind it, the curiosity is there.
From the start the BNB blockchain transaction fees were not free. It's just lower than Ethereum blockchain transaction fees. However I don't know which platform you are using so argue that the BNB blockchain transaction fee is free. The increase in BNB transaction fees increases with the increase in BNB prices. As with previous Ethereum blockchain transaction fees.
other factors are usually caused by transaction density, I mean the more people make transactions on the coin (BSC) or on the BSC network can affect the transaction fees as well. but for me personally gas cost in BSC is still cheap compared to Ethereum Network. if you are interested then you can use the solana blockchain, matic or fanthom. gas cost on their platform is also cheap