I have never heard this before, and there could be some truth to it, but I mostly disagree. The Italian Renaissance began before 1453 (the year that Constantinople fell). The economic and political situation (war between Milan(typical monarchy situation) and Florence (republic-like), economic collapse during the BP, economic regrowth, etc. which inspired investment in art and culture). The influx of scholars from the east may have had an influence, but not significant enough to be the cause of it.