You can authorize future share sales well ahead so that you're already prepared. Many companies have consistent authorization to sell into the market when they feel timing is right. It's a common way that BDCs and REITs grow. If the stock is trading well above NAV, selling shares is accretive to shareholders. Buybacks above NAV/fair value are dilutive (which clearly was the case with BBBY)

You can also sell in blocks to private acquirers if anybody bites. But the first approach is better if it's a meme situation (no rational buyer would take a block of shares close to market). Clearly there are many companies that could have and likely still can sell large blocks of shares close to market, NVDA being one example.

"A shelf offering allows a company to register its securities with the SEC but then delay putting them on the market for a period of up to three years. This provides some advantages, as the company can time the release of its securities, ideally aligning the issuance with favorable market conditions. Shelf offerings can also help companies save on the registration process, as they do not have to re-register each time that they release new shares."

from Investopedia

Somehow people confused this all along the way and simply equated "buybacks = good". Its about what value you get for the shares you're buying/selling. That's it. Buying back your shares at a 30x+ earnings multiple is going to be a terrible allocation of capital for most companies in the long run