Unable to auto mount a data disk from /etc/fstab but mounts with mount -a command

Here are the commands I ran:

~$ lsblkNAME    MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTloop0     7:0    0 63.3M  1 loop /snap/core20/1852loop1     7:1    0 49.9M  1 loop /snap/snapd/18596loop2     7:2    0 91.9M  1 loop /snap/lxd/24061sda       8:0    0   30G  0 disk├─sda1    8:1    0 29.9G  0 part /├─sda14   8:14   0    4M  0 part└─sda15   8:15   0  106M  0 part /boot/efisdb       8:16   0   75G  0 disk└─sdb1    8:17   0   75G  0 part /mntsdc       8:32   0  128G  0 disk└─sdc1    8:33   0  128G  0 part

as you see, sdc1 is not mountedthen I run

dev-mio-admin@mio-vm:~$ sudo mount -a

and

dev-mio-admin@mio-vm:~$ lsblk

and we can see sdc1 is mounted to /mnt/disk1

NAME    MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTloop0     7:0    0 63.3M  1 loop /snap/core20/1852loop1     7:1    0 49.9M  1 loop /snap/snapd/18596loop2     7:2    0 91.9M  1 loop /snap/lxd/24061sda       8:0    0   30G  0 disk├─sda1    8:1    0 29.9G  0 part /├─sda14   8:14   0    4M  0 part└─sda15   8:15   0  106M  0 part /boot/efisdb       8:16   0   75G  0 disk└─sdb1    8:17   0   75G  0 part /mntsdc       8:32   0  128G  0 disk└─sdc1    8:33   0  128G  0 part /mnt/disk1

Here is the line in my /etc/fstab file

UUID=1c0adda6-1cc1-450d-89ee-76d26d384b13  /mnt/disk1   ext4   defaults   0 1

Why wouldn't it get attached automatically?

Thanks beforehand.