The Conservatives were in power at "federal level" (UK/Westminster) for a decade and a half, and were only booted from office last year. If anything we lead the Oz and Canadian results.

The Tories are so on the nose that Farage's mob (reform), who have been nibbling away at the Tories for near 2 decades are now getting a look in, it's a bit analogous to the tea party take over of the GOP.

So the more populist flavour of the Tories will take seats off the Tories - it looks like a massive shift but it's not really. The massive shift was a few years ago when the Tories managed to swipe a huge amount of the Labour voting base with populism - Reform are now taking a subset of that - the remainder having unhappily returned to Labour (who are doing a shite job and are basically red tories - ie Tories in Labour jerseys)

TL;DR - everyone (80%) are massively unhappy with the Tories, the left parties are doing a very mediocre job of addressing it, so an alternate "Tory without as much of the privileged upper crust running it" party are stealing their votes

Hell, it's more complicated than that but that's as good a distillation as I can do in a couple of paragraphs