So, you mean you
1) shutdown the pc
2) removed the HDDs
3) started up the pc
4) shutdown the pc
5) reinstalled the HDDs
6) started up the pc => pc not booting (so you have raid5 as root, right?)
Not sure if it was a good idea to run a fsck -r.
Once 2 HDDs out of 4 failed because of my controller blowing up and the pc didn't want to recognize the raid5 anymore, and I was able to fix it and be able to access all the data with: (I then took a note of what I did
If in a RAID array two HDDs or more fail / get an unhealthy status at the same time, there is the possibility that something might have gone wrong with the drivers of the controller. Try to restart the array with all the HDDs (e.g. a RAID 5 with 4 HDDs)...
mdadm --assemble --force /dev/md0 /dev/sda1 /dev/sdb1 /dev/sdc1 /dev/sdd1
...and check in "cat /proc/mdstat" if both the HDDs are still marked as "failed". If not, try to re-add the faulty HDD with...
mdadm --manage /dev/md0 --add /dev/sdd1
...or whichever HDD failed and see if the RAID rebuilds correctly and still works afterwards.