https://www.independent.co.uk/news/world/americas/us-politics/trump-harris-2024-live-tim-walz-jd-vance-news-b2592431.html?page=2#post-1690388
Former president repeatedly uses immigration to bash Harris in marathon 59-post social media trolling session as she accepts Democratic nomination
american culture frowns down upon talking about politics in public and that's created an entire country of people who lack the practice in engaging in meaningful political discourse so now it's devolved into nothing more than looking for a chance to dunk on your opponent; arrogance and condescension are great ways to dunk, especially if you're a lawyer who has lots of practice doing so.
My theory is that they kept Biden in the race as long as possible before swapping him out with Kamala so that they could try and coast on post-biden enthusiasm before she talked too much.
they also let the opposition spend millions on attack ads that now have nothing to do with the opponent