INDIAHERITGAE

Yes, as the name suggests let us share our views about the ancient indian culture, what it was , what it is now and what will it be
There is a sloka in valmeeki ramayana
which reads-
viSwaamithrasthu dharmaathmaa labdhwaa braahmaNyamuththamam
poojayaamaasa brahmarshim vasishTham japathaam varam
(read with varamozhi)
which means Viswamithra on getting brahmanyam- means after becoming brahmin, worshipped Vasishta.
As we know Viswaamithra was a king- kshatriya, and there was a tussle between these two on account of Kaamadhenu.
Now how viswamithra became a brahmin? Is it possible as per the norms today?
If not then why vaalmeeki wrote in his ramaayana such a verse?