Why are Tories suddenly blathering about supermajorities?
Constitutionally there's no significance in the UK. Practically a landslide just means the government doesn't need such tight party discipline to get its legislative program through the Commons.
"Supermajorities" is American slang for one-party rule common in state legislatures.
Example, Tennessee. The GOP has a supermajority so it can expel representatives of their opponents at will.