TCP/IP is the network protocol, along with the routing protocol BGP that make up the internet. TCP/IP succeded XXX on the internet. Because of the rise in popularity of the intenret, TCP/IP is the most popular networking protocol of all time. There simply is an amazing amount of OS's and platforms that support TCP/IP.
The most popular implimentation of TCP/IP came from the 4.3 BSD release, because of the BSD copyrites people were free to adapt the software to their own needs.
Vint Cerf is largely credited with creating the protocol.