In the Download Options panel, an ArcGIS Online feature-layer-based item shows a KML download-file size of 175 MB. Then, when the KML is downloaded, the size of the downloaded file is much larger--1,336 MB--when it lands on the local computer. Why might the file size of the downloaded file be so much larger?
Also, QGIS crashes when adding the downloaded KML file. The KML file works okay in ArcGIS Pro (after waiting a while for it to load).