The variance in potential outcomes of holding VOO is much, much lower than the variance of holding crypto.

Buying VOO buys a share of the profits of the work of many millions of people. It also speculates that other people will continue to want to buy those profits.

Buying a token only speculates that more people will want to buy that particular token. It's much harder to project that people will continue to want it.

Oh yes. So that's why half-half.

A risk parity approach would say more like 95% to 5%, but that works too.

Oh sure, one half can be bigger than the other half.

A 401K is a box, not a specific investment. You can put things like VOO in the box. Anything in the box is tax advantaged however.

Tax advantages basically mean you make the dollars invested inherently worth more

Tax deferment and stability.

And hopefully, taxes will be same or lower when you retire.