Right now is an attractive time for an IPO because valuations are really high. Every asset has gone up this year--bonds, stocks, crypto, real estate, oil, commodities. You really only get to IPO once and when you IPO you want your share price to be as high as possible.

Some of the equity holders in Coinbase will sell some of their shares personal shares. Even if they don't sell their own personal shares. Just the Coinbase corporation selling shares will dilute the current owners. During the IPO the owners can also sell their personal shares and make some money. They probably won't fully exit from crypto i.e sell ALL of their shares, but they will probably sell some of their shares.

The other nice thing about being public traded is getting to sell your own personal shares on an exchange. There are laws that limit private equity investing. If your company stays private--it kind be hard to find buyers for your shares and get a good price because there are fewer buyers in the private equity market.

What is nice is that once Coinbase is publicly traded. The SEC will require all of the C Suite executive to report the sales and purchases of shares. So if the people at the top of the company sell, you will know.

Will this attract outside investors? Yes, it will because when Coinbase sells shares they will have to sell them as stock and not coins. The stock market has rules on this. Coinbase will have to report audited financial statements. There are some people who will not invest in anything without reading financial statements.

The other thing to think of is that Coinbase the exchange as a stock should be thought of slightly different from Coinbase the stablecoin. I don't know how much of the Coinbase stablecoin is owned by Coinbase the exchange or what governance looks like, but people who are buying the stock mostly care about the exchange. Its like buying oil pipelines doesn't mean that you own any oil.