That's just natural selection though. Albeit driven by us. Families (or loners as the case may be) go for the dogs with those characteristics. Then those pets, more than the other ones, survive and breed. Eventually the big eye/head gene is prevalent.
Unless you're saying that dogs go around trying to widen their eyes as much as possible while thinking "I'm well cute like this, mustn't blink".
Not quite.
Apparently the genes for tameness, especially in dogs, also affect genes controlling appearance. As the animals, over generations, have become tamer for our own needs, it seems they unwittingly also become more and more 'cute'. It's been suggested this is because tameness is something associated with juveniles, who also have the same 'cute' appearance, and that there is a connection in the genes for these 2 attributes. This has then, just from this simple appearance trait alone, essentially put them in competition with children, as they stopped being solely effectively a tool and more of an emotional bond.
In our endeavours for natural selection of tameness, we initially unwittingly ended up making dogs look cuter, and as we then adapted them into companions rather workers, we started to exagerrate the offshoot of 'cuteness' more and more.