Maybe i missed something important but why was Pence expected to challenge the electors?

I read the section in the Constitution i heard people use as justification for this and i can't see anything there supporting Pence actually doing what was, for some reason, expected of him.

So am i missing something?

Let me add that I don't care about Pence at all, I don't like his politics, I don't like him, and I am very okay with him having no political future. The part that does bother me, though, is that im pretty sure i just watched a guy get loaded with false expectations and then railroaded, which is a bigger issue than Pence to me.

Election fraud must be fought but can it be done by trying to get people to throw unconstitutional hail marys and then drumming them out when they dont?