The problem with Kenney is that he is personally very unpopular. He has a loyal inner circle, but there is no voter block that particularly likes him. The "Kenney Party" would have zero support. Things would be different if Kenney was seen as a centrist who personally attracted broader support than his party (like Notley). Of course, in that case, he may not have faced a UCP rebellion to begin with. It's a lot easier to start attacking your own leader when you smell blood in the water (or are looking at a 20% approval rating).
The problem is, Kenney has zero authenticity. When he shifted from federal to provincial politics, he positioned himself firmly as an unapologetic conservative populist, adopting this ridiculous Ralph-Klein-meets-Brad-Wall "Alberta redneck" persona, complete with a pick-up truck. But then he turned around and started hurling insults at the rural grassroots, calling them "lunatics". He might as well have quoted Hillary Clinton's "basket of deplorables". Throw in his anti-Asian comments during the pandemic and he's alienated virtually every single voter block across the province. All this, and we haven't even gotten to the actual policy disasters and scandals of the past four years, which would have strained the support of even a personally popular leader.