The issuance of CBDC is a huge publicity for digital currency. When CBDC is issued, many people will learn about the existence of digital currency, and thus will also know Bitcoin, a digital encrypted currency. There may be ordinary people who understand digital currency because of CBDC, but they may like to invest in Bitcoin.
It may only play a superficial propaganda role for cryptocurrencies, but the central bank and their digital currencies will never do anything for Bitcoin. They will think that cryptocurrency will threaten their projects and will be detrimental to the development of CBDC itself.