If you trade in a regular brokerage account, every sale is a taxable event--i.e., if you sell a stock and had capital gains that are taxed, you owe taxes on that--even if you used those funds to buy GME and lost all those gains, plus some. (This is a common mistake that day traders make--they don't reserve funds for taxes, and end up owing much more in tax than they ever withdrew to their bank account).

Not so in an IRA. You'll only ever be taxed on gains (in a traditional IRA) when you withdraw money to your bank account.