Some characters actually lost their support at some point. Back in the days, when people saw that Golden Saw had NOTHING in Smash 4, they kinda gave up. That's why I always said that Isaac's performance in the ballot was always overrated. Isaac's fate is the saddest because he lost some support when he needed it the most. That's why he came back as an AT and not as a playable character. Now, his support is better than ever and he's back in the spotlight thanks to his AT. But if many people didn't stop to support him during the ballot days, the sad truth is that he would probably be playable right now.
Decidueye's support died too. Geno's support was weak during Smash 4 days.
So yeah, there's always a base of hardcore fans who will keep supporting their character but most of the time, the majority of the people are just bandwagoning. That's the case for Erdrick and basically every other characters.
Truth is, before we started talking about Erdrick, the vast majority of the community didn't know who the **** he was. Most of the time, when people talked about DQ, they just said "we want some DQ representation" or "Slime could get in" at best. No one was like "What about Erdrick ?". So yeah, there's a lot of bandwagoning with this character. And I'm pretty sure that if he's not getting in, people will forget about him and just ask for "Dragon Quest representation".
And I love Dragon Quest and Erdrick, I have no problem with him being the Square rep, so don't start using the "hater" argument.