Remember, Trump's on-board with Ryan on this (even though Ryan nominally warned against the decision). Kellyanne Conway said this morning on GMA that ditching oversight was necessary because "there's been an overzealousness in some of the processes over the years."
As I wrote last night, the last time the GOP achieved unified Republican control in Washington, their first move was to loosen ethics oversight. First they pushed through the "DeLay Rule", which allowed House leaders to stay in their leadership roles while under indictment. A couple months later, when putting through the rules for the new Congress (the same step that happened last night), they created another new rule which held that any question that deadlocked the Ethics Committee was automatically dismissed. In other words, unless a member of the party of the person being investigated was willing to support the investigation, it was automatically dismissed.
This is what happens when Republicans take over. Are there crooked Dems too? Absolutely. Rep. Bill Jefferson was the poster boy for that back in the era we're discussing. But when the Democrats got unified control of the government in 2007, they did just the opposite. They created the Office the GOP just effectively killed.