By Luc Olinga Crypto buying and selling platform faces falling trading volumes as digital currency prices fall sharply. Can’t blame Coinbase (COIN) for trying. The most popular of the crypto exchanges in the United States is scrambling to try to find sources of growth as trading by retail investors has slowed markedly. It is these same investors, led by young people who have suddenly become rich thanks to their investments in crypto, which had fueled the crypto mania in 2021. But since the records reached in November, the euphoria seems to have died down. It is the hard return to reality. Bitc…