System crash - strange chars in syslog

That syslog file content you are showing us of all zeros is indeed corruption of the filesystem/syslog writing.

Your system crash caught the system mid-writing to the syslog file, and that is the end result.

Already have seen it happening several times over the years, in Linux VMs and a couple more times in Raspberries and Banana Pis.

Nothing to obsess (too much) about or lose a lot of time to investigate why you have this for a one-time event. I would be more worried at finding out why it crashed, especially if it is a regular event.

PS getting into anecdotal territory, last time I had this happening regularly in a Banana Pi R1, I managed to trace the cause to a (faulty) realtek wifi chipset.

To slightly expand on that answer, your syslog have the content of a page of memory partially committed to disk, with the metadata of syslog not up to date. That string of ^@ chars are actually NUL bytes; exactly what a freshly allocated page of memory initially contains.