Need to be more specific but if you're asking about how launching new coin won't inflate the supply of bitcoin (i guess?) the answer is simple, by launching a new coin you don't inflate the amount of bitcoin in circulation but you're creating an entirely different network detached from bitcoin, it has nothing to do with bitcoin and your coin will more likely just become another shitcoin.
There's reason why bitcoin's hashrate produced hardly can be replicated.
You are absolutely correct in stating that the launch of a new coin will not affect the Bitcoin supply. What is happening is the creation of an independent blockchain network, complete with its own consensus and security mechanisms. This has nothing to do with the mature Bitcoin protocol and its inviolable supply of 21 million coins. The difficulty of replicating Bitcoin's hashrate is a clear testament to the power of its decentralization and global distribution. Thousands of independent entities worldwide contribute to the security of the Bitcoin network, making it highly resistant to attacks and manipulation. A new coin, regardless of its intentions, must build a foundation of decentralization and trust from scratch, a monumental task that can never "add" value or scarcity to Bitcoin's already proven value.