At 4:11 PM on Tuesday, Stefan Coolican's phone started lighting up. It was WhatsApp — the crypto chats he was in were getting all worked up because, finally, an exchange-traded fund for bitcoins was coming to the U.S., making it much easier for Americans to buy the cryptocurrency in their brokerage or 401(k) accounts. "Everybody was sending this tweet sent by the official S.E.C. account," said Coolican, a former trader and investment banker who has since co-founded Noble, a crypto technology company. "Today the S.E.C. grants approval for #Bitcoin ETFs for listing on all registered national securities exchanges," it read. Below the statement was a photo of Gary Gensler, the chair of the Securities and Exchange Commission, next to a bland government-speak statement about transparency, efficiency, and regulation. Coolican checked the price of bitcoin — up about 2.5 percent to about $48,000, nice — then went back to work. After all, the approval process had been going on for months, and the announcement wasn't exactly a surprise.