I see that your occupation is landscaping.
Yes maples are 'outdoor' trees. They belong "outdoors". Even baby ones. That's where they were born. That's where they live. All year long.
In winter they go to sleep. They need their sleep.
In spring they wake up again.
Please put it back in the ground for 5 - 10 years.
Then try to make an outdoor bonsai with it.
Japanese - outdoor - really