Can Bitcoin continue as usual without a hard fork and without the core maintainers and their access to Bitcoin Core’s GitHub repository? A hard fork is out of the question since it will not be Bitcoin anymore.
Yes it could continue without core maintainers but like the name implies they are quite important in maintaining the bitcoin software and addressing bugs.
Not to mention it could lead to stagnation in its development.
Mind you there are other contributors that could help with development but won't be as efficient.