Putting on my tin-foil, devils-advocate hat... AKA I don't necessarily believe this but I also have no counter-argument:
Mostly performative. When it's decided that something actually needs to pass, then you'll get some sacrificial lambs that vote across the aisle. Typically they'll be close to retirement or from a state where they won't be heavily punished for that specific vote.
I would think at least some of this should be obvious, but I guess not?
From a political standpoint, the statement "from a state where they won't be heavily punished for that specific vote" is a weird way to put it, since if you framed it in a positive light it would sound more similar to "the state population falls on both sides of the issue and thus either vote could make sense from their legislator depending on exigent circumstances and other factors" or any number of other explanations depending on the vote and populations.
Please explain how that's "exactly the same".