Perhaps that is the fault of a deficient classical education, rather than the merit (or lack thereof) of Bergson's ideas? To extrapolate from your example argument, there are thousands of historical figures you have never heard of. And yet, their decisions and actions have had a profound effect upon trajectory of history, and the way the world appears to you today. Are they unimportant just because you have yet to personally learn about them?

Or perhaps it is a lack of imagination: Bergson was certainly a large part of the intellectual milieu in which Einstein was working. His thoughts pushed Einstein in certain directions Einstein might not have gone otherwise. Even if Bergson is unremarkable for his own work, surely he is important for no other reason than his impact on the thought of the remarkable and memorable theories of Einstein?

Taking 'I haven't hear of them' as your starting point of historical importance seems like an intellectually lazy argument to me. Each to their own, however, and you are certainly entitled to your opinion.