Mark fits a lot of information into one sentence, at the clear expense of poetic polish. He switches between three different constructions: hypo+genitive, meta+genitive, and then the change of subject putting him into the dative.
Writers have always avoided this - but it was slightly more important to Greek ones because of how the language relied on word-endings. Listeners and readers were prone to lose the sense if they misheard or misread one letter, so good prose tries to keep the constructions consistent which helps signal to the reader. In polished prose we'd expect structures more like "Jesus was tempted by Satan, threatened by beasts, and helped by Angels".
English does have the same - so it does come across well in translation. It might be an affected clumsiness - like when witnesses want to make sure nothing is left out and don't let themselves consciously embellish the story.
Mark doesn't describe these things because he doesn't know. And by this phrasing I think he wants to have made clear to us that he doesn't know.
It won't be unintentional crudeness. Mark is often setting up such beautiful structures, in both the said and the unsaid, that he doesn't want to let the phrasing distract from them.
Here there is probably a balancing of Satan - beasts - Angels
Σατανᾶ καὶ ἦν μετὰ τῶν θηρίων καὶ οἱ ἄγγελοι
That's subtly hidden in the construction. And it makes the word ἔρημος ironic. This place is far from empty.
Or at an overarching level: the angels here at the start of the gospel might balance with the white-robed man at the end who says "He has risen!"
Angels are mentioned by Jesus in a few places, but Mark otherwise keeps them back until the end. There they go from being a mysterious thing seen only by the anointed - to a physical reality. And it's not just that image, Mark 16:6 also picks up the tone of Mark 1:13 - by not saying it's an angel (because he doesn't know). The desert and the tomb are both private to Christ, but we can enter the tomb.
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A problem in translation is that τῇ ἐρήμῳ doesn't contain the "wild" in our "wild beasts". It's wilderness as in the empty place without people and buildings. And to say "wild" beasts is adding an adjective that English needs for clarity: Mark doesn't need an additional word here. Obviously these aren't cows and sheep, in this context the word "therion" excludes those - but it's not that the lions and snakes and whatnot are markedly wild, or any wilder than they usually are.
Also about user19086's point that therion is a diminutive of ther=Monster... In Lidell & Scott that's the third sense of the word. Ther was mainly wild animals you can hunt and it extends from there to things like sphinxes and Cerberus. And it gets overtaken by its diminutive - like we no longer sense the diminutive in the word "movie".