Gnl Cariappa and Thimmiah are Coorgis, whose language is closer to Tamil than Kannada. Raja Ramanna and Kasturi Rangan are Iynegars who speak tamil at home. The largest IT head honcho (Ramadorai) is Tamilian. Speaking of which, Infy CEO Nilekani is a Konkani. Wipro chief Premji possibly can't say more than beda, beku in Kannada. Many IT CEO's and senior honchos in Bangalore are Tamilian/ Northie. Most IISc scientists / profs are migrants from other parts of India. Kannadigas are a small minority even among the IISc students. Many other Kanndaiga celebrities you did not mention are also of varied stock: Tulu speaking (Aishwarya rai, Prakash Raj), Marathi speaking (Bhimsen Joshi and many other musicians), Tamil speaking (Masti, AK Ramanujan and many literateurs), Telegu speaking (M. Visvesvarayya), and so on.
If your definition of Kannadiga includes all those living in Karnataka at any time, then that's really great, and I truely appreciate it. But I doubt if many of them, especially the successful lot in Today's booming Bangalore, can speak Kannada.
Tamilians are one of the most globalized community, you find them in most every country living peacefully in their adopted homes. Them not learning the local language is an incorrect statement from an ill-informed person.
