Anatolia was Rome. Most of the investments were done here right?
Lets think of the major cities.
Trebizond+Smyrna+Ceasare-Iconium area+Amasias+Sinope+Nicomedia+Nicea VERSUS what? Thessaloniki+Athens+Epirus+Adrionople? Nothing significant in Peleponessos area.
The Roman towns in Anatolia were much more crowded, rich and diverse(hence more trade)
+Major trade routes in Anatolia
+More population in Anatolia
+surrounded by sea, feels safe. Mountinous Greece part is also safe but it is not easier to develop, build roads...etc
+Eastern influence and trade, very important (by that time)
+Armenians and Georgians as a barrier with others
+More production, more income
+Anatolia is fricking awesome...AWESOME. Be jeolus
If Constantinople was the brain, Anatolia was the heart.
(also interesting info: There are more Roman theatres in Anatolia than in Italy, and more Greek theatres again in Anatolia than in Greece) I cant confirm it right now though, but makes sense.
Both the Greeks, Romans and Greek-Romans invested in Anatolia.
They not only migrated but also Hellenized most of the people. When someone says East Rome to me, the first thing that comes to my mind is Anatolia.