Having trained real horses, why are we now training racehorse girls after time-traveling?

On that day, Ryuji Wada, Kenichi Ikezoe, and the younger Takatoshi Imamiya, who had been in the Uma Musume world for some time, gathered again to discuss their recent discoveries.
Ryuji Wada: You might not believe it, but I found a great opera at Tresson Academy. However, she has become someone I hardly recognize. In my memory, even if she became a horse girl, she shouldn't have this kind of personality.
Kenichi Ikezoe: Don't even mention it! You should be secretly happy. I've also encountered the Golden Master and the Eastern Merchants' Reform, and the Guild Master even specifically asked me to be their trainer. I'm going to suffer again. I really just wanted to be a True Mecha trainer...
Then, the two former riders looked at Mr. Takatoshi Inamami standing to the side and asked in unison: "Grandpa, why aren't you saying anything?"
However, the now-younger Grandpa Jinlang silently took a sip of wine, and after an unknown amount of time, he spoke:
I met the Golden Ship, who was just as mischievous as the horse I knew back then. But ever since I became her trainer, she said she would send me back to Mars with her.
Ryuji Wada and Kenichi Ikezoe: ...
This is the bizarre story of two famous GI horse breeding horses (lol) and a stableman who traveled to the world of Uma Musume.