Can someone explain to my silly little brain how a tech (Bitcoin) developed over 10 years ago still remains somewhat safe. Meaning, why people are not fully able to hack your wallet (cold or not)..? Was it that well build in the beginning?

I have little to no technical understanding of the blockchain. I do however believe that I understand on a larger scale the concept of what Bitcoin is, De-fi , blockchain, ''insert other buzzword'' here. But I can't explain to my limited technical mind why there is a common understanding that you can buy crypto and have it stored somewhat safe. Like that original wallet, the first one with millions in it, that was open in 2009..... how has this not been hacked? More than 10 years later and it still as safe as in the beginning.. ? I am 100% sure I'm missing a big feature of Bitcoin here... Help :')