Remember that the extradition bill was indeed shelved before things went very, very south. The key objective had been achieved, except that it had now become only one of "the five demands," with "not one less" open to discussion. (Anyone who doesn't get the reference can look it up.)

The HK Chief Executive had already set herself up as a sacrificial lamb, taking full responsibility for the failed extradition bill. In theory CCP could have let her step down, sticking to the script that she had acted on her own, and a return to status quo might have been possible.

This would still have required some CCP willingness to compromise, but the withdrawal of the proposed Article 23 bill in 2003 and CH Tung's eventual resignation was a precedent. The violent metastasizing of the protest movement, and in particular the direct attacks against Chinese sovereignty e.g. attacks against the liaison office, combined with calls for US/UK intervention more or less removed that option from the table.