Why does Steam pause downloads while my NVMe SSD hits 100% usage?

The 100% figure represents active time, not necessarily maximum transfer speed or temperature. Steam may be downloading, decompressing, verifying, and installing files simultaneously. A DRAM-less budget SSD can become saturated during that workload, especially when its cache is exhausted or the drive is fairly full. The faster internet connection may simply expose the SSD as the new bottleneck.

The drive is not automatically dead, but 90°C was definitely too hot. At those temperatures it can throttle itself, which would explain the pauses. Around 65°C with the heatsink is much more reasonable. Check the SSD's firmware, make sure it has at least 10–15% free space, and monitor its SMART information for media errors or other warnings. Back up anything important in case its condition gets worse.

The advertised sequential write speed is not what you should expect during a Steam install. Game downloads involve lots of smaller writes and file decompression, and the SSD may be handling several operations at once. Once the fast write cache fills, a low-end drive can slow down dramatically, so Steam pauses until the SSD catches up.

A 500 Mbps connection is about 62 MB/s, which sounds easy for an NVMe drive on paper, but real game installation is more complicated than one continuous file copy. The SSD can still be the bottleneck during decompression and file processing. Using an HDD would not really be an improvement for modern games; it would usually make loading and installation slower.