I don't believe RM, JJ, etc. didn't research the market and public opinion before making the move. They probably did but nonetheless were convinced it would be fine. Convinced by support of EPL clubs. EPL clubs were instrumental for UEFA to manipulate Perez and Angelli into acting quickly to discredit the idea of the Super League before it became real. RM, Barca, and JJ are vulnerable now and it was used against them. BM were prudent enough to stay away from this dirty story.
EPL club were always against ESL, because it was a threat for their league. Now the problem is solved. They and UEFA are obvious beneficiaries of everything that happened these days.
I know, it looks like a freaking conspiracy theory, but that's the only scenario in which Perez and Agnelli at least don't look like absolute idiots.