>>718643448
They don't
They want to infiltrate the society above ground with a plan that goes something like this:
>take key people from established, meaningful settlements and replace them with synths
>this synth infiltrator slowly takes a more friendly stance towards synths in order to slightly nudge society towards being pro-synth over time
>finally present the Institute to the people above ground with a grand "gotcha! see, you were living with synths all this time and you didn't even know it, so why wouldn't you be able to do it now that you know?"
in order for man and machine to co-exist
however, the Institute does not view synths as human, they are still very much scientists and they consider it just as ridiculous as the Brotherhood does that anyone could possibly even think that a machine has genuine feelings and emotions, so the end result of their society would basically be Blade Runner, which the game took a shitton of inspiration from
but unlike the BoS they don't realize that they're playing with apocalyptic levels of fire (why the fuck would the synths be content to live out their days as slave labor and not just rebel) just like the people playing around with atomic energy, because they're fucking scientists
kill all scientists, the HECU were right