> Then if you're at that local maxima, then yeah you're gonna cater to those fringe elements because those are the only votes that are left you can get. You've burnt the bridge with the rest of the electorate.
The way election strategy works can sometimes be unintuitive.
1) Not every demographic votes at the same rate—the "youth vote", which is a lot of people, famously, barely matters. "But they won it for Obama in '08!"; firstly, no, actually, he'd have lost a couple states without them but still would have won; secondly it still wasn't all that good; and thirdly it promptly plummeted again, there was no staying-power.
2) "Off-cycle" elections tend to be ignored by moderates and have low overall turnout.
3) Primaries are A Thing, and you have to win the nomination (determined almost exclusively by committed members of your own party) before you can even attempt the general.
4) The "true swing" segment of voters—the ones that both claim not to be committed partisans, and also don't consistently vote exactly as if they were committed partisans (that is, aren't lying or deceiving themselves when they say they're swing voters)—is itty-bitty, and they are practically all, in the language of political science, "low information voters" (and, yes, you can just treat that as a euphemism for "morons"). There's less to gain from directly courting them than one might think, and courting them doesn't necessarily involve, like... good policies. Or even being connected to reality. Even more than other aspects of campaigning, it's mostly about name recognition, good acting, and marketing.
What does all that mean? The name of the game is GOTV (Get Out The Vote). And suppressing same for your opponent. You don't ignore everything else, exactly, but the person who gets more of "their people" to the polls is very likely to be the one who wins, not the one who sways fence-sitters. Notably, achieving this doesn't necessarily require targeting even all of your own party.
> Every wedge issue slices of x% of people
Some are immensely effective. I listened to way too much of NPR's post-2016 "holy shit, how did this happen?" interview series with Trump voters, and, over and over, people said "yeah, he sucks, but I prayed on it and stopping baby-murder was more important". That single issue is a giant GOTV driver and excuse to do whatever the fuck else they want with their policies, for Republicans. I haven't looked into the data, but wouldn't be a bit surprised if their pro-life stance is a lot more effective, by those measures, than the Democrats' contrary stance.
> DeSantis and Trump (and most of the Republican Party) have been chasing a local maxima as of late
Trump's campaign was revolutionary. The way he built his platform was exactly like he'd walked into a rural diner, struck up political conversations, wrote down all the ideas he heard, then just said those things. This is, it should be noted, a lot different from the usual Republican platform (this is likely why they didn't bother to assemble an official party platform, as they usually do—they didn't want to codify his in any way, but also couldn't contradict it). The reason the normal platform can differ so very much from what their voters want, is because of how US elections are structured (the two-party system) which strongly tends to produce situations like that. Trump just said "yeah, fuck all that" and said exactly what Republicans wanted to hear.
The rest of the party is still trying to figure out what that means for future elections, and the future of the party. DeSantis' whole mess is part of that effort, I expect.