BSC is indeed a newcomer when compared to ETH, but BSC has the advantage that it has a relatively stable and cheap gas fee
With that advantage, many new projects use BSC to make their smart contracts, which makes BSC better for now and becomes the toughest competitor of ETH which has too expensive fees in my opinion.
If you only rely on low costs, it will be very difficult for BNB to fight ETH, because Polygon also has a much cheaper cost compared to BSC, but Polygon is still not able to compete with ETH, and for ETH the price is already very expensive now it's still very reasonable for the current transaction fee problem, now try to imagine if the price of BNB can be equal or the same as ETH, will the cost also be cheap ? I don't think so bro.