Entirely different explanation:

1. India sets up the first few research organizations in Bangalore. - IISc, DRDO, HAL - decision being entirely strategic to keep them away from Pak. nukes.

2. Some engineers think too much on the long lunches afforded by most govt. sector instituitions and see an opportunity in exporting software. One of these guys is narayan murthy.

3. Infosys is born and soon Patni, TCS and Wipro - each drawing from talent pool of DRDO, IISc and HAL. Obviously most start in Bangalore.

4. Engineers from across the country flock to these new high paying jobs. Some again extend their lunches too long.