Solved but not explained: Qt5.5 webkitwidgets, missing DLL, unexpected crash - c++

Question

I made a very simple and boring postal code -> city lookup program (it uses an online api).
I wanted to add functionality which allows to select any country (which the api can process). For this I wanted to load the main page and parse the DOM to get all the countries. This requires webkitwidgets. http://www.zippopotam.us/#where (this is the table I want to extract the information from)
Unfortunately, when attempting to run the program it never even starts and gives me the Application Output:
Starting ZipcodeToLocation.exe...
The program has unexpectedly finished.
ZipcodeToLocation.exe crashed
So I try running the debugger:
An exception was triggered:
Exception at 0x77cbd4f2, code: 0xc0000135: DLL not found, flags=0x0.
During startup program exited with code 0xc0000135.
Weird... so I try finding this error message on the internet and nothing really helps me. I think maybe I set something up wrong, so I open the webkitwidgets examples and compile those. When attempting to run - same error.
Using programs like some dependency walker didn't really help me much either.
I ran the MaintananceTool to check whether I was missing something, but I wasn't able to detect anything.
Im running QtCreator on Windows btw.
My .pro
QT += core gui webkitwidgets network
CONFIG += c++14
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
TARGET = ZipcodeToLocation
TEMPLATE = app
SOURCES += main.cpp\
MainWindow.cpp
HEADERS += MainWindow.hpp
FORMS += MainWindow.ui
If I remove the following portion from my main window ctor, everything runs es expected:
auto page = new QWebPage(this);
page->mainFrame()->load(QUrl("http://www.zippopotam.us"));
Note: this is currently the only section using webkitwidgets.
I would be really happy if someone could help me overcome this roadblock and has any suggestions on what might be going wrong.
Edit: Just to make it complete, a screenshot of the depends run: https://i.imgur.com/YWpdlO6.png?1
The german part translates to "The System can't find specified file".
Edit2: If you have QtCreator installed and want to attempt reproducing my error, create new QWidgets application, edit your .pro like so:
QT += core gui webkitwidgets
and this line at the end of MainWindow ctor (probably any usage of webkitwidgets would do):
#include <QWebKitWidgets>
//...
QWebPage *page = new QWebPage(this);
Edit3: As a reaction to a recent comment, I tried copying all dlls from the Qt directory to the .exe location (release) and tried running it from there. It said "Missing Qt5Positioning.dll". Which is weird, because I am not using the location module... But I guess that explains the missing dll crash?
Edit4:
I finally had enough and simply completely reinstalled Qt from scratch. Somehow my installation had to be messed up, because after that the problem vanished.