Why fsck would have run after the reboot? Compare your /etc/fstab entries against fstab - ArchWiki… only a zero in the fsck position disables it, and typically a zero is only used when what’s being mounted is a network drive (not internal).
Why it would have found garbage? Failing drive, improper shutdown, etc…
If you are a user who crashes their PC (i.e. kill power) when it “freezes” and not using REISUB… what you’re doing is likely the cause, and you need to read/implement [HowTo] reboot / turn off your frozen computer: REISUB/REISUO