Looked him up, I'm sure they took him because they thought he would be useful vs the Soviets. Real life intelligence gathering before the advent of satellites, spy planes etc was a grimy business, many grimy people were employed in the post WWII era against what was an existential threat to the US. Lots of less than stellar people are used today, particularly in HUMINT, as they happen to be the ones who know things or are saleable. Just look at our spies, the Walker etc. It is a crappy business using crappy people but the way of the world is crappy people are useful to the extent they can be purchased. An overall amoral attitude is helpful in spies selling out their country.
I’ve been reading a lot of Clancy. He goes into how intelligence officers operate. It’s similar to what cops do with confidential informants but against sovereign governments and the stakes are much higher.
Here’s one problem, you’re paying out all this money to your sources, black money, not traceable, it’s got to be tempting after a number of years to start pocketing some of that and then you’re just as bad as your spies.