Because you aren't taking demographics into account. Trump's supporter skew older, so they are quite literally dying off. Also, his supporters, young and old, are unvaccinated and refuse to wear masks. COVID deaths are so much higher in red states that the average lifespan is now 4 years less than in blue states.

Trump is losing a lot of support, even among MAGA enthusiasts. I have written a lot about it. He has also lost the support of the evangelicals now that Roe has been repealed.

Keep an eye on his crowds. They are steadily shrinking. The pro-Trump crowds were so pathetic outside the Manhattan courthouse when he was indicted, that they were outnumbered by the media.