" The case of Peter Mandelson, who resigned from the Lords in February after revelations about his friendship with the late sex offender Jeffrey Epstein, drew renewed attention to the upper chamber and the problem of lords behaving badly."
I think this was the "Aha" moment that the critics and backers to push through the final "death blow" as it were. There's always an incident/scandal that brings the final straw. Over the years, there were always calls to dissolve the House of Lords, but nothing really came to fruition, until Peter Mandelson. He became the "limit".
I have to always grin because in the years reading about the Royals, I've read plenty of stories concerning MP's of various political parties in the Commons "behaving badly", "Do as we say, not as WE do."