I found about the Wario Land series by Youtuber Whoisthisgit, and he did a video on Wario Land 4. I got interested in the series after looking into the games, and playing them The reason I like Wario is his greedy, funny, weird, and cool personality. He also is relatable at times, as for liking money and garlic, and being selfish at times.
When I bought Wario Land Super Mario Land 3 back in the Game Boy era. Took me a while to get into it too, so it was probably the second or third playthrough that really made me like this series.
That said, I suspect Wario Land 4 had a bigger effect though, since not only was it a game I was super hyped for in the day, but one I played over and over again, to the point I could possibly call it my favourite game of all time.
I became aware of Wario through a copy of SM64DS I was loaned as an elementary school kid, but paid him no mind (I remember thinking he was kinda scary). Years later I got WarioWare D.I.Y., which sparked a small interest with me in terms of making up lore for the characters... mostly other than Wario because I liked their unique designs so much. I also played WL4 on the 3DS Ambassador Program and it grew to be one of my favorite platformers. The original WarioWare was also included in the offer and I beat it several times (once I did it in a day).
My interest in Wario as a character came during the whole Waluigi craze of 2016-ish, which caused me to wonder where all the love for Wario was, since his games were so much more influential to my younger self. Did a ton of research and played a lot more of his games (through Virtual Console, though now i'm collecting physical copies), and here we are today. I started to appreciate him more than just some gross anti-Mario. I mean, he is that, but he's also more than that.