Why exactly is New Brunswick so linguistically polarized?
More due to fact Blaine Higgs doesn't speak French and was a candidate for Confederation of Regions party (anti-bilingual party) back in 90s so not trusted by Francophones to respect their rights. In Anglophone areas, he won big more because he handled pandemic well and he promised steady leadership, no rocking the boat which is I think what people want. Some like Bernard Lord have broken linguistic divide and indeed if PCs had a bilingual leader who performed as well as Higgs they might have won a landslide similar to Lord in 1999. So while true Francophone areas tend to be more Liberal than PC, a different leader could have done better.
For Anglophone areas, Liberals have pretty much lost connection so need to figure out what they stand for and have an appealing platform. Obviously by nature the rural southern areas are always going to go PC, but the middle belt and urban Anglophone ones could go Liberal with right leader and right policies.