Investors in MicroStrategy will think like they might have double ROIs by holding the stock.

Because
If they simply buy Bitcoin, they will have only one profitable asset, bitcoins in their wallets.
If they buy MSTR, they will have two profit sources: one from bitcoin and another one from MSTR stock. Because MicroStrategy is a company that provides other products which can bring benefit to their company and investors. Bitcoin is not the only one product MicroStrategy has.