After any object on the stack has finished resolving, the active player gets priority. This means, that if the stack is empty at that time and it's currently a main phase, the player can start casting a spell or playing a land without another player having the chance to act first. And in the case of an instant or a card with flash, you won't be able to snatch it period even if it's not a main phase or the stack isn't empty.
If a card is put into the graveyard during any phase other than the active player's main phase (but during his turn), and is not an instant or a card with flash, then the other players will get at least one chance to interact with the card before it can be played as no step/phase can end without all players passing priority on an empty stack first.
If the stack isn't empty, the active player won't be able to play any card requiring sorcery timing, and other players can interact with it before it can be played.
In general, it depends on whether the game gives the player controlling Crook of Condemnation priority between the time the desired card is in the graveyard and the time the player controlling Muldrotha has priority to play that card (and all requirements for playing that card are met).
In your example, assume you control Crook of Condemnation and your opponent controls Muldrotha and hasn't played any cards yet this turn. In general:
If your opponent casts Entomb any time they could cast a sorcery, and puts a land card into their graveyard when the spell resolves, the stack will then be empty and your opponent will get priority again. The opponent could use that priority to play that land card.
If your opponent casts Entomb in response to another spell, or if they do so when it isn't their turn, and your opponent puts a land card into their graveyard when the spell resolves, the opponent will afterwards not be able to play that land card yet, since the stack isn't empty or it isn't their turn, respectively.