Nobody watched the original syndication of the anime. It was very niche. The games are what sold Pokemon. The anime got a boost from the games. Sure, maybe there were some kids that watched it but it was the games that really sold kids. The real reason Pokemon got popular is because they were simply the best Gameboy games out there at the time. There wasn't anything else like Pokemon out at the time. Pokemon was... surprisingly complicated and complex for a Gameboy game. The internet didn't exist and exploration was 90% of what made it so interesting. You never knew what was coming next. Heck, kids thought the glitches were secrets to find out and made up all kinds of fake nonsense.
The anime didn't really pick up speed until it changed channels and networks the following winter after the game's release. What happened was Pokemon after the game release got a lot of spread over the fall, and into Christmas it was on every kids Christmas list. The come the winter, the zeitgeist picked up steam. The anime also didn't make Charizard popular. He was popular because he was a giant fire breathing dragon. Then the anime shoved him down everyone's throats.