The compensation for working in those fields is often that you're working alongside other smart people, in a situation where your work is highly valued.
The money is just a factor in the equation, money equals respect in a lot of different ways.
People want to work on projects where meaningfulness and respect flows to them. Money is one of the things you want to see flowing.
Crypto offers that money, and offers a lot of technical challenges because programming distributed systems that must be error free is tricky.
In terms of the ad tech, a lot of the work on ad tech happens because Facebook/Google/et all have cultivated environments that offer that kind of respect, and offer serious technical problems.
Advertisements per se are not so much a part of it.