It sounds like you don’t understand how movement politics works. Questions have been posed to Bernie time after time how he would govern with a Republican senate. Oddly, he receives this question a lot more than any other candidate.
He is going to use the large apparatus he has built since 2015 to mobilize people to action. Rallies, marches, phonebanking, running for office, and so much more. Obama had something similar brewing but he abandoned this when he entered office. Change happens through a large number of people demanding it. Moderate Senators working in Congress rarely get anything of substance done and maybe you’re okay with that.
Frankly, it’s just lazy to compare Trump and Bernie and you’ve done it again, sadly.