Theresa May’s strategy recently seems to be to sit as still as possible so no-one notices she’s there. That way she hopes to stay in the job as long as possible, until she can eventually say, ‘Well, we had some difficulties, but we somehow managed to muddle through’.
But that’s not going to work, because while she’s just sitting there not uttering a peek the Remainers and the EU are scuttling about, busily preparing ways to screw us over. And the Brexiteers can see this. So, while it’s risky to dump her given the tiny, fragile majority the Tories have, which is vulnerable to just a handful of Remainers voting the wrong way, she has to go, because otherwise the Remainers will win anyway.
If she dumped Hammond she could possibly survive, but as she’s clearly unable to do that, she’s toast.