In a nurshell: About every 4 years there is the "halving" event, that means the block subsidy (reward when someone finds a "block", that is how Bitcoin are created) is halved. So only half the amount of #Bitcoin per block that used to be mined can be mined from then on. That means the "inflation" is halved. and thus a scarcer supply while demand remains constant or increases. That means increasing #Fiat prices. News about the halving event and continued governmental #Fiat printing, inflation, increase of cost of living etc. (increasing M2) brings Bitcoin to mainstream, prices rise, people get greedy, prices reach an ATH during a bullrun, OGs cash out, prices decrease/fall to about the level of the ATH of the previous circle (bear market), Market waits for the next halving.