You're welcome, it is a question that had once crossed my mind too.
Well Dajjal is a man, he will be born of a woman and live a normal life until the trial. So in islam as you know, we believe that every person has freewill...
The prophet pbuh warned us about the signs and tribulation that will occur in the lead up to Qiyamah. The hadith which details all of this was in essence, a window or a peak into the future. So it isn't that God had determined Dajjal to be the chosen one...but Dajjal would be presented with a trial (the gift of powers and global influence) and he would choose to mislead people to the fire...so that hadith is a glimpse of one of the things that Dajjal will choose to do when presented with the choice of either committing Kufr and shirk or deciding to do good...
God Almighty is showing us what He knows will happen based on Dajjal's character and lack of deen and the prophet pbuh was warning us to not trust him...
It's not that God chose Dajjal...He has allowed Dajjal to act upon his freewill as a human. When we pray or make dua, it is an opportunity to seek guidance and help from the Almighty in an attempt that whatever decisions we make in life are the best for us...dua can change what you would have chosen to do if God wills...
I'd just like to add that Isa (as) hasn't yet fulfilled his duty as The messiah and this event is vital as it concludes his role and thus he can pass away after living out the rest of his days...so with God Almighty, the bigger picture is also something we need to remind ourselves of...
It is a pretty big and complex topic so I would urge you to maybe speak to your local ulema for a more detailed response if you still have some queries.
Hope that helps!