Sort of like when you have a ton of currency floating around, it doesn't buy as much.
With a few dozen million shares, there is not as much to sell and buy. Reducing the shares "float" tightens up supply and more likely to be captured by long investors with a longer horizon. With hundreds of millions of shares float, more shares are available for anyone who thinks they can divorce their company thesis from their company CEO thesis to throw money at it, and think both their divergent theses will prove correct because reasons.
I.e., with less shares float, less room for anything other than smart money--but minimal float by itself is no guarantee of success, far from it.
The flip side is that as a company's value increases, float can be too low and the individual share's expense can eventually price out retail traders.
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