Let's assume you are airborne in a hot air baloon above a cloud deck in a 50 kt wind. The balloon has zero airspeed of course, as do the clouds, so as you look out over the side of the basket nothing appears to be moving - not you, not the clouds. Then the clouds disperse... and you have a view out the basket of the ground rushing past at 50 kts!
That's an excellent choice of scenario SSD. If we go back to the start of that balloon flight it demonstrates my point very well. I can't imagine anyone would want to launch a hot air balloon in a 50 knot wind, but as you've suggested those conditions let's go with them.
Before launch the basket is tied to the ground. Ground speed is zero but TAS is 50 knots (Produced by of the wind). The balloon would be leaning downwind quite markedly.
We release the tie-downs and the balloon starts to rise. As it rises it accelerates downwind. GS increases and TAS decreases. After a while the balloon is moving downwind at the same speed as the wind, so the TAS is zero and the ground speed is 50 knots. We have gone from a situation in which we had zero GS and 50 TAS, to one in which we have 50 GS and zero TAS.
The only thing that could have caused these changes in TAS and GS is the wind. If the wind accelerated the balloon, the balloon must have experienced the wind. In this case the wind was steady.