If they're a new DM, they could be having "new DM syndrome", where-by a person that assumes the power of DM gets on a power-trip.
New DM's may get it into their head that it's "them vs. the players", so, with an endless supply of monsters and what-not, just keep throwing things at the players to "beat them". Then the DM gets a quick rush of satisfaction, and a player group that never wants to play with them again.
Or, the new DM may get into "new toy syndrome", where there's so many new bells & whistles for them to play with, they think more about trying them all out than about how it's affecting the party.
Both cases are bad DM's.. and incredibly bad DM's are both (wanting to try our new things to keep destroying players).
Remind the DM that it's not "DM vs. players", because that isn't fair at all. You, the players, have a finite amount of resources you can muster. The DM, however, can keep pulling however much stuff he wants out of his/her a** to destroy you.
That's not fair. I mean, if the DM wants to go that far, why not just summon a magical god ray from the sky that smites all players. Why beat around the bush?
Oh, right.. b/c the power-monger DM wants to feel like they "beat you fairly". But, like I said, it's not fair. They will just keep throwing things at you to wear you down and prevent you from recovering until eventually the part wipes.
You'll be able to tell this kind of DM when they get all giddy at how badly the party has gotten their butts handed to them. Also, if the DM shows no remorse (or even a sense of pride) at PC deaths... those are huge red flags.
The goal of DM'ing is "it's all of us making a fun adventure", and the DM is the guide. The DM controls opponents, yes, but they are just part of the guided tour the DM is giving for the adventure.
The DM's role is:
story-teller ... get you interested in the adventure
cat herder ... guide you along when you're off the beaten path
flubber ... secretly flub die rolls that wouldn't provide enough challenge, or would lead to too much challenge
The DM is a shepherd. The players are their flock. A good DM remembers the goal is to make a fun & exciting experience, not to become a god that smites.
But, when new folks get into that seat, they can get so focused on the power or the fun stuff they can do, the players take a backseat. The players should be front-and-center to the DM's concern all the time, not disposable punching bags.
Another way to think of this... mobile gaming has created toxic game enviroments where whales or hackers create uber-characters. All they do is wait for fresh meat noobs to show up, so they can flex on them with their uber-characters. All this does is create a toxic inner circle of uber-players that run off new players, and the game dies sooner or later when it gets a reputation for having a toxic uber-player base that just meat grinds new folks.
A person can be like that as a DM, and that's bad. They may look down on the players and just think of them as punching bags to take their frustrations out on. That creates a toxic game environment that players soon leave.. unless the DM shapes up or someone else takes charge.