This was likely planned for more than a year. Probably since Lily's graduation or even before.
Here's Aviel's tweet announcing the re-debut plans in January of last year:
The article in the tweet was deleted (probably got lost when Idol remade its website) but there's an archive
here.
View attachment 65721
He goes in more detail about re-debut plans during one of
his newsletters 2 months later:
View attachment 65725
The issue isn't that Brave was involved but more so how long it took. Aviel said more details would be announced a few weeks afterwards but there was nothing. People were thinking August might be the month since both Katta and Nikki's birthdays were then, but the only thing that happened was Katta got birthday merch that maybe showed a new design. After that, it was more nothing until the announcement yesterday. That's more than a year of mostly silence. Maybe the Israel situation was messing with their plans but who knows? The reception to the announcement seems to mainly be positive at least.