This is it. This is the final act. This is that moment. The GOP has nowhere else to go. The shutdown was that final line and they had to cross it. There was no other choice; it's all they've got left.
Boehner could have called a clean CR to the floor and it would have passed and then there were only two outcomes for the GOP:
1) The Tea Party primaries Boehner and every GOP congressman who voted to pass the clean CR. Many of them win and win the general. Many also win the primary and then lose in the general and the GOP gets to watch as the Dems enact their dream agenda the final two years of Obama's Presidency and the voters realize that's pretty cool and the GOP is toast.
2) The GOP finally fractures and the main stream (such as there are) GOP reps tell Boehner to cut the Teabggers loose and they start caucusing with the Dems for all intents and purposes (they might even be able to hold off a teabagger House leader if they stick together). This effectively creates a third major party that sucks off 20-30% of the GOP vote and the Dems really seize control and, again, the GOP is toast.
or...
Keep sending bills that are doomed to fail to the Senate and shut down the government. Then hold their fragile, fracturing coalition together as long as they can; try to convince enough people the shutdown was the Dems fault, the ACA sucks, the GOP is their only chance to get it stopped and hope things work out in their favor when the ballots get cast.
The key word in that final sentence was "hope".
Boehner was left with the choice of shutting down the government or being the guy who finally killed the GOP. He's an ineffective putz but he's not stupid and there's no way he wants to be "that guy". Of course he has no one to blame but himself. He's the guy who sat idly by and let the Teabaggers run roughshod over his leadership. He could have stood up years ago and started working to educate the voters on the way government is run. He chose not to do that. Now the beast is loose and it's devouring it's master. Egged on by talk radio and FAUX news the base will be heeded or it will take its pound of flesh and then some.
There were several reports of GOP reps smelling of booze in the final few days leading up to this. I don't know if that was to steel their courage to stand together or to make it possible for them not to care enough to cross this final line. Either way they are toast and the more rational members of their caucus know it, but it's not like they had a choice, It's all they had left...