In an uptrend, all along the way, demand is greater than supply. As long as the demand is greater than the supply, the uptrend will continue.
When people are optimistic, they become overly optimistic and they will overbuy. That’s why we have overbought situations. When the market is overbought, it does not mean that it will immediately fall. It may continue to be overbought for a long time.
When demand slows down and supply increases. The uptrend will be halted. As the supply becomes more and more and demand less and less, the trend turns down.