I know nothing about economics or finance, but how is it that the first $1T dollar company was Apple and that didn't happen until 2018 and now it's a $5T dollar company just 8 years later. Did Apple really become 5x richer in that time?

No but people have to bet all their money to get rich and retire early so everyone is leveraged and pumping the stock market

Apple seems to be well positioned to profit from AI without investing to much. Other major companies are very AI exposed and people like Apple positioning.

Generally lots of money flowing around bidding up the top companies.