Prosimians on average are not as intelligent as their simian counter parts with the notable exception being lemurs which live in semi large groups. what I want to know is could a group of prosimian conveniently evolve human level intelligence and what evolutionary pressures would lead to it?
Yes, and some groups show particular potential in that direction
There are a group of lemurs called the Archaeolemuridae, the last members of which which died out approximately 1280 C.E. Compared to other lemurs, the two genera of archaeolemurs (Archaeolemur and Hadropithecus) were adapted for life on the ground, highly omnivorous, and had a very monkey-like skull. Despite being lemurs, archaeolemurs had brains which were more comparable to monkeys, though on the low end of the scale. What this means is that there was nothing really stopping lemurs from developing bigger brains (you already have lemurs convergently evolving with monkeys in brain size), and it is possible given the right environmental stimuli that they could have developed sapience like humans.
Indeed, given that archaeolemurs are characterized by having dropped down from the trees and adopting a more terrestrial lifestyle, you might even get a sapient species from them that somewhat resembles humanity in many features (though bipedality is a stretch given that baboons and ringtailed lemurs have a similar evolutionary history and are quadrupeds).
However, at the same time the archaeolemurs seem to have developed one of the same weaknesses that characterize humans and other large primates: they reproduced very slowly and had long juvenile periods, likely due to their larger brains, and this may have been one of the features (along with human hunting) that wiped them out.
Yes. By the same pressures we did.
That might sound trite, but evolution is a powerful force, and the only set of circumstances leading to our level of intelligence is our set of circumstances
So take your lemurs. Force them into grasslands for a while. Expose them to coastlines and oily fish. Give tool users chances to shine.
Eventually smart gets rewarded, and you end up with human level intelligence.
But I’d question if you’d call them prosimians by then...