With these strategic seconds and some sincere firsts, the unworkable transitional state can win by Condorcet's rule. A stalemate continues until enough voters decide it is hurting everyone. Ensemble rules may reduce grudging compromises by electing a chairperson who has an electoral incentive to balance each policy. It is not to satisfy a mathematical abstraction about proportionality. It is to enact broadly popular, central policies that make most people happier than the status quo.
Ensemble councils make that more likely.
The potential good of a PR election is cut short if it is followed by one-sided majorities for making laws and appropriations. No, every PR council has a ruling majority of the left or the right which excludes the second-largest party from decisions. There is no active swing vote. Central parties are rare in PR parliaments. Germany's Free Democratic Party may be the only powerful one.