Gulf money has been a big contributor to the progress Kerala. But it is really remittances from abroad - it means from wherever Malayalis have stepped out to - that is behind it.
However it is only one of the reasons.
But the standard of living has gone up. People live long. Educational and medical facilities have improved and are available everywhere.
The income of people has gone up manifold in comparison with what it was 50 or 60 years ago.
There has indeed been a social upheaval that has brought Kerala on par with developed nations though no one in Kerala or non Keralites everywhere else would concur.