New bands collect likes and followers before officially recording and releasing music to build a base, just like they said. You have just discovered an incredibly normal, mundane part of the human condition.

You had the choice of simply ignoring the invite and wondering why you would have liked it, or asking someone familiar with bands why they sent you the invite. Instead, you decided to send a message showing that not only made fun of people working hard to achieve their dreams, but also clearly demonstrating that you are not intending to be helpful.

Plenty of other people who liked that band probably have no idea if they really like it yet or not, but they're being minorly helpful by keeping the like up. You were one of the subset that actually decided to be explicitly unhelpful.