Most of users only see hardware not software and they buy Chinese phones. In comparison Samsung lacks performance and offer old SOCs in budget devices and the difference between these two are only Processor. Given that point "Performance" Chinese OEM's take advantage of this by offering more powerful chips in budget devices.
Actually, (I don't do gaming) Samsung do a great software optimization for any phone. Chinese give you a great SoC, my friend bought a Realme 8 5g and it was not par expectations.