Resigning like this, ie no known scandal or medical issue, is virtually unprecedented and has everyone in DC scratching their heads. Conceivably the motion to unseat him as Speaker was going to be a lot closer vote than people were saying. If he kept his Speakership only through democrat votes and was rejected by a majority of the republicans, it would have been very embarrassing for him personally and would have left him with no real authority.
He apparently felt strongly that a government shutdown as unacceptable, which left appeasement of Obama as the only alternative. That alternative was fine with Bohner's wing of the party, the Chamber of Commerce, country club, K Street republicans. It was not OK with the Tea Party/Ted Cruz wing. Perhaps Boehner saw nothing but unappealing options, so chose to go out in a way that preserved some dignity for himself and let him claim the moral high ground. And slide easily into a high paying lobbying job.
He apparently felt strongly that a government shutdown as unacceptable, which left appeasement of Obama as the only alternative. That alternative was fine with Bohner's wing of the party, the Chamber of Commerce, country club, K Street republicans. It was not OK with the Tea Party/Ted Cruz wing. Perhaps Boehner saw nothing but unappealing options, so chose to go out in a way that preserved some dignity for himself and let him claim the moral high ground. And slide easily into a high paying lobbying job.