Though it's not a guarantee, analyst stock ratings upgrades generally don't happen in a vacuum. They tend to follow improvements in fundamentals, strong earnings trends, or other catalysts that could reinvigorate a company's outlook. This tends to get retail investors to look more closely at those stocks, which can in turn drive purchases and, potentially, share price increases.
StubHub Holdings Inc. (NYSE: STUB), Targa Resources Corp. (NYSE: TRGP), and Equinor ASA (NYSE: EQNR) have all recently experienced analyst upgrades, although for different reasons. In each case, the company may be showing signs of righting some of its underlying issues—or of continuing to improve upon aspects of its operations that have already been going well.