Weak typing is fine, and even beneficial for small scripts - what javascript was originally meant for. It does not scale though. It leads to large projects becoming unpredictable, unwieldy and mired in technical debt.
A poor programming language does not entirely preclude the possibility of a successful app, it just makes it a lot more difficult to release a stable one.
For companies that can throw huge resources at their apps (e.g. google) the language deficiencies do not matter as much because they can be dealt with with extra work and testing.
Wait, what....