Dunno. I suspect it's because they know it'll pass, and it's a calculated move to try and not look too soft on crime. If both their votes would have meant it's defeat, you can be sure they'd have voted the other way.
It's going back to the Assembly, because one Senate amendment stuck to it, pretty innocuous as best I can tell. It changes the exceptions for "police in their duties" (Can't shoot a cop who has articulateable probable-cause, and in the course of his duties kicks down your door, and use Castle Doctrine as a defense) and replaces "police" with "Emergency Services" to cover fire fighters and EMT's.
My understanding is that Castle Doctrine does extend to your car now as well. Effectively making it a "Make My Day" Carjacking Law like some other states have. However, the "Stand Your Ground" removing all duty to retreat in public when you have a legal right to be there never got added in, like some preliminary rumors had been hoping it would.
The lack of "Stand Your Ground" to coincide with CCW is disappointing, but I can live with it. WI doesn't have a big legacy of prosecuting self-defense, and anyone with two brain cells to rub together can figure out how to use our "reasonable man" standards to their benefit. "I had my kids with me and couldn't run", "I have arthritis", "I have a heart condition", "I was afraid if I turned my back on him to run, he'd get me" etc. etc. etc.
The main thing I'd miss in public self-defense not in your car or home is the civil liability protections. Although a bill that adds complete civil immunity for any legit self-defense could be passed later.
