One caveat I didn't list is my direct manager was one of those that left as well, the next higher level manager oversees all of the engineering teams and has been incredibly hands-off since the team manager departed.
I will hit all three as you've raised an excellent point: having options is probably more important now than potentially having leverage come review time.
Personally, I do well with benign neglect, so this could be a good setup for me. Spelunking in code I didn't write is fine for me too.
However, this relies on having a reasonably clear idea of what your code is supposed to do, how to deliver changes, authority to make decisions and access to the tools you need. If you don't have the stuff you need and you don't have an accessible manager either, you're going to have a hard time staying positive and doing good work.
Did you talk to other companies before taking this job? If so, let them know you're open to offers.