We don’t have a 2 party system. We have a political class constituted from a duopoly and collusion by the dems and repubs.
My bet is that the repubs decided to pass this, and 14 members were chosen/ assigned to vote with the dems. (safe seats/time until re-election/retirement plans)
The best way for a ruling elite to hold onto power is to create the false illusion of pluralism and choice. With rare exceptions, Democrats and Republicans stand for the same things. Most of their differences are about inflated rhetoric and matters of emphasis rather than substance.
The same interest group can hold onto power in spite of a shift from R to D every 4 to 8 years. When things get bad, people blame the R and replace it with a D, and vice-versa, not realizing that they are switching teams under the same management.
Nothing makes this sham more clear than the current "bipartisanship" on amnesty for illegals.