The way I think it works is each government starts with a finite amount of political capital after there is a change in majority. This is expended and used up o

The way I think it works is each government starts with a finite amount of political capital after there is a change in majority. This is expended and used up over time, slowly in a growing stable economy, much faster when there are destabilising events. Delivering Brexit and mitigating Covid were massively destabilising events that required an enormous amount of political capital to deliver. On top of that you then have scandal after scandal which drain that political capital. Ultimately the Conservatives are out of political capital. They can only regain it by not being in power for a period of time.