It starts to when you ask yourself: Where else are people meant to store money? Since interest rates and bond rates were at historical lows. So you have people who are looking at 10% YOY returns on one hand and 0.2%/2% on the other and making the rational decision.
Does this make stocks overinflated? Yes. Is it going to suddenly pop? Unlikely, since the conditions that caused it won't suddenly change (e.g. certain bonds have ticked up 1%~ but taken months).
Does this make stocks overinflated? Yes. Is it going to suddenly pop? Unlikely, since the conditions that caused it won't suddenly change (e.g. certain bonds have ticked up 1%~ but taken months).