EU referendum, brexit and the aftermath

I'm not knowledgeable enough to comment on all* of those PMs, but wasn't John Major appointed at the end of 1990? He then called an election in 1992. Clearly the appointment of a new (majority) party leader = a New PM, but that doesn't effect the argument over whether an election should be called to allow the population to ratify that decision.

*Brown was a mupet and should have blaitently immediately called an election, rather than waiting until everyone hated him and be bullied into it. However, in his case there is a strong argument to say the country knew he was to be Blair's successor and most actually expected Blair to step down well before he did.