The technologies used in Bitcoin have also been in development for several decades, and by 1998 the first cryptocurrency was already released, according to a quick search on wikipedia.
Note the difference - "technologies used in Bitcoin were in development for X years" vs. "Internet as a whole concept of network of network was in development for Y years".
No, the internet as we perceive it today, as a global network, didn't exist back in 1969. The technologies we use in internet today were developed back then, though. Just like they were for bitcoin (cryptography, merkle trees, etc)