Why did the Thing alien even bother trying to assimilate the men?

Sometimes, it's best not to ask questions when it comes to fiction.

Because the plot required it.

it was hungry? i know it didnt eat them , but maybe it was going to , or do some alien equvalent.
Maybe it ate their minds ....

Because it felt less vulnerable while hiding in an imitation than it did out in the open. Imitation gave it its best chance to survive or escape the south pole.

It did not account for man's capacity to distrust one another.

Because that's what makes the movie great. That you aren't sure who is infected by the Thing and who isn't.

My guess is that it probably figured it couldn't successfully escape without assimilating/killing all the men at the base first. Notice that the dog-thing doesn't assimilate its first victim until after Mac and Copper bring back the split-thing corpse? The camera lingers on the shot of the dog ominously looking at the situation. The thing probably knew that the humans were smart and would soon figure out how the thing worked by studying the corpse, and would then turn their suspicions towards the dog next. It probably had to spring into action and assimilate some people before being discovered, which it probably knew would inevitably happen.

I suppose it could be possible for the dog-thing to just sneak around the base for weeks scrapping together pieces necessary to construct a spaceship in incognito...

So it could hide? Why do animals use camouflage?

Or maybe it consumed them for nutrients. Not enough information is given about the biology of the Thing to make any definite conclusions

OP assumes its intentions. Never addressed in the movie. Complaint disregarded.