I think there's more compelling evidence that voters switched. The main argument I've seen that Dem turnout was the issue is that Trump "kept" a similar number of voters in total, but that's kind of begging the question.
So for example the Nevada guy, Jon Ralston, looked at early vote patterns in Nevada, and based on that, concluded that Harris would win. But she lost. This is what he said afterward:
Biden got 522k votes in Clark County in 2020 and Trump got 431k. If you multiply that by the population growth of the state (seems to be around 5%) you'd expect D/R votes in 2024 to be 549k and 453k respectively. But Trump got 482k votes in 2024. That's 30k more than expected. Harris got 510k, which is 39k less than expected, and 11k less than Biden. Trump had to make up that difference somewhere, and since votes for 'other options' also decreased from 2020 to 2024, the answers are either 'from people who voted Democrat last time' or 'from people who never vote.' The first option is likelier (though there's surely a bit of everything).
Generally there's been some pretty big shifts in counties, states, demographic groups. If you remove 1 vote from column D and make it disappear, it only has about half the effect of moving it from column D into column R. So it starts to get pretty unlikely that these big shifts are just from turnouts.