I’m not quite sure the conclusion matches the data. Obviously it matches “so far”, but… while I follow UK politics, I’m not versed well enough to confidently address my theory, but I feel that if this was US Presidents - the system is broken, and so no matter the party of the President, the oligarchs ensure they are the only beneficiaries of government, so satisfaction drops from the intiial hopes after election to the reality that our democracy is broken.

I wouldn’t be surprised if there is a similar effect in the UK is what I’m saying.