Is it possible to see the rank of all players in previous matches? I forgot to check the ranks at the end of my last match
This is not possible.
But you can download your previous matches for a replay. For that you have to go to the "Watch" menu in the main screen. (Top red circle in the following picture.)
There you can see your previouses matches and with clicking on them you can download them. If they're download, you can click them again to see a dropdown menu where normal replay watching is possible and to only watch your highlights in that match. (Lower red circle)
If you watch your highlights, the whole match will be replayed, but scenes where you don't kill or don't plant/defuse a bomb will be skipped in high-speed.
If you press tab to see the score board in replay, you will only see your own rank.
FYI: If you tab to score screen while replay and click on a player, then "CS:GO profile", it will open the Steam Community profile instead. So this is not possible, too.