The first Texas Holdem tournament ever held was WSOP. But the idea appeared much earlier. In 1949 Benny Binion was asked to stage a high-stake poker marathon. He agreed. This marathon lasted 5 months in public view. Johnny Moss had won $2 Million in this marathon. And the only thing that his opponent Nick the Greek had said was: "Mr. Moss, I have to let you go". After that he went upstairs and fell asleep.
In 1970 the first WSOP event was held. It was at Binion's Horseshoe again and again Johnny Moss was the winner.
Since that year the WSOP tournaments have been held there each year. Getting he golden WSOP bracelet, which receives the winner of the main WSOP events is the highest honor for any poker player.
However, poker owes it's popularity not to WSOP but to World Poker Tour, the televised series of poker tournaments held all year round since 2012.
A lot of tournaments nowadays are held online. There are various other televised poker tournaments like European WPT etc. Many of them have very low buy-ins and some do not have them at all, so everyone can have a chance to participate.