How did Byler start?

So I watched ST since second season release but I was never involved with the fandom bc I’m already in many others and also wanted to avoid spoilers/leaks but now bc it’s the last season I joined and omg to my surprise I’m shocked how byler became so popular bc I could have sworn everyone shipped Mileven back in s1&2. Now I’m more curious does anyone know when this shift happened where many bylers came out of nowhere? I know s4 kind of started bc one sided crush Will has on Mike but WHAT TF HAPPENED IN THESE PAST YEARS? Anyone explain pls bc I feel lile I’m watching different show than bylers.