Where can I see data showing those major spikes from after RH and YK as well as the high numbers from after Sukkos.
I beg to differ. It's convenient to blame the spike on the people who didn't take precautions seriously. I hate to break the news, but there are not plenty of people who all of a sudden started doing so. For starters, Simchas Torah was mostly business as usual.
The OP specifically referenced EY, and the data on case spikes in the first half of Tishrei there is readily available. Further, there is documentation of a clear difference in approach in shuls, schools, and individuals between RH and YK, and through Succos. There were also clear indications of precautions being effective, based on communities where they were taken and communities where they were not (see case numbers in Mizrachi communities). Also, I clearly said there was no spike at Succos, only that there continue to be new cases. From the 10th through the 19th, Israel added 16k cases. A definite drop, to be sure, but it didn't just disappear.
Even in NY/NJ, there were definitely changes in many, many shuls in how they handled the lead-up to RH, and even RH itself, to how they dealt with the rest of Tishrei. Outdoor and tent minyanim were very common, and many higher risk individuals took additional precautions. Were there plenty of places that didn't change at all? Sure. I think you'll find higher infection rates in those shuls, either from the first wave or the previous 45 days (Elul through YK). You want data that doesn't exist, though, so anecdotal evidence, first wave estimates, and extrapolations from State data are going to have to do.