It boils down to C compatiblity, every non zero numeric value is true, that language where good developers make no errors.
In this case the expression has type bool and the underlying object has type int, so it is a straightforward strict aliasing violation.
With GCC you can compile with -fno-strict-aliasing to ignore this rule. But now you fall afoul of the rule that prevents accessing an invalid representation (i.e. a trap-representation) of an object. This rule is also described in the link I posted before, under the object representation paragraph.
Even ignoring both rules, there is still no reason to expect the assertion not to fire:
int x = 2;
assert(*(bool*)x == true);
float x = 2.0
assert(*(int*)x == 2);