who is maybe the perfect reflection of what everyday conservatives have become, ignorant, stupid, and incredibly well off while whining about how they’re not well off enough.

I wouldn't say they're that representative of a lot of everyday conservatives. A lot of them are doing pretty poorly, but they're ignorant and get pissed off at the idea that anyone else might benefit from a program they personally don't qualify for or disagree with. My father is absolutely convinced that if the Democrats had the political will and ability to implement a wealth tax, that he would somehow be absolutely murdered by taxes on his $10 or $11 an hour he's making at a Winn Dixie in Florida. He's also the sort convinced that welfare queens living it up with brand new cars and designer clothes are not just a real thing, but a common thing that happens that Democrats just don't want people to know about. He'd probably also chalk up his retirement sucking due to what limited social safety net we have in the US, rather than him draining his retirement accounts while he was unemployed before hitting retirement age so he could play golf and go hang at the bar with his buddies even though he was broke. Medicare is his right, though, he worked for that and earned it, but screw these poors under 65 trying to get healthcare with Medicaid. About the only thing he's missing for your average, everyday conservative is an unhealthy dose of religion.

Having two of the most charismatic Presidents in American history

Lincoln and JFK? No, wait, the two Roosevelts? No, Reagan and Lyndon Johnson? Jefferson and Washington?

If you're talking about Obama and Clinton, sure they were relatively charismatic compared to boring presidents like Bush Sr., Jimmy Carter, Gerald Ford and Richard Nixon. But, US history is filled with very charismatic presidents. Even Bush Jr. was fairly charismatic, that's how he managed to rile up the country to take part in the "War on Terra", and how showing up at ground zero and putting on a hard hat was so important for so many people.

The problem with Jeb Bush wasn't George Bush Jr., it was Jeb Bush. He wasn't very charismatic, wasn't a deep thinker, wasn't a leader, etc. The Bush name isn't toxic among Republicans, it's just that Jeb has even less charisma than Hillary Clinton.

As for what killed the GOP, it's much more complicated than just two somewhat charismatic Democratic presidents:

• The financial crisis, and how the US focused on stabilizing the banking system without also helping the little people
• A black president, driving racists to the GOP and making them determined to vote
• Centrist presidents taking fairly moderate economic policies, destroyed the GOP's image as the party of fiscal responsibility
• Clinton and Obama not shying away from military solutions to problems made the GOP's image of the hawkish party weak

So, when the GOP was at a period where it was trying to figure out how to define itself, Trump arrived and defined it as the anti-establishment, dog-whistle racist, christian theocratic party.