What factors facilitated the rise of the Godwins and why did Edward the Confessor allow them to become so powerful?

Don't forget about still reliable fear of Danish supremacy (remember Danelaw). Edward was never confident of his regin, all his activity was to secure England and protect kingdom against Danish pretenders. So I guess he didn't care about local landlords so much as we use to think.
It was Anglo-saxon tradition to have many local powerfull lords/earls as well. There wasn't England in our common meaning untill Wilhelm's time. There were many freshly joined kingdoms and lordships if it makes sense.

[…] Don't forget about still reliable fear of Danish supremacy (remember Danelaw). Edward was never confident of his regin, all his activity was to secure England and protect kingdom against Danish pretenders[…].

Interesting suggestion but probably valid until the time of the death of Magnusson. Besides, while the above seems true of the earlier stage of Edward’s reign, one cannot assume that it holds good for the latter part of it. Edward’s precarious hold over pre-conquest England, which no doubt remained in constant danger of a Scandinavian invasion, became much more secure after 1047.

[..] So I guess he didn't care about local landlords so much as we use to think.

I think he did yet he probably either had no other choice but to rule with powerful lords or he pursued a pre-meditated policy of governing through power-sharing.

[..] It was Anglo-saxon tradition to have many local powerfull lords/earls as well […].

England was hardly unique in this respect. Similar developments were clearly visible on the Continent.

[…] There wasn't England in our common meaning untill Wilhelm's time. There were many freshly joined kingdoms and lordships if it makes sense [...]

There certainly was. England as a concept existed prior to the invasion of 1066. Looking back one can only speculate which concept of England (Anglo-Saxon or Norman) showed greater vitality in folk memory. Until the end of the last century, the Anglo-Saxon perception of history and England tended to separate it from the rest of Europe. However, with the process of European integration well underway, the Norman input (read French or continental) is being re-evaluated. Though separated by the water and often classified by various English historians as 'different', England is undoubedly getting 'closer' to Europe.