If the stock is trading at $120/share that means everyone who owns stock (and is paying attention and offering it for sale) won’t sell for less than $120. But t

If the stock is trading at $120/share that means everyone who owns stock (and is paying attention and offering it for sale) won’t sell for less than $120. But that doesn’t mean all of them, or even most of them, would sell for $120. Many of them probably believe their stock should be worth more than $120 and expect the price to go up in the future. So if you want to buy out the whole company you have to pitch a price high enough that a majority of shareholders (or the board of directors as their fiduciary proxy) agree to sell at that price. This is basically guaranteed to be a substantially higher price than whatever the current market price is, because if the average shareholder didn’t expect the stock price to go up, why are they holding shares? As the deal becomes increasingly likely to go through, the stock price will likely gradually shift up to match the deal price.