When Jamie Dimon visited Boston in 2018 to herald the first Chase bank branches here, he described what seemed like an impossible goal. Even for America's biggest bank. The JPMorgan Chase chief executive said he would not be satisfied until his company is among Boston's top three banks. Now, less than five years later, Dimon is closing in on that goal. JPMorgan's takeover of First Republic on Monday suddenly gives it a big market share here, The Boston Globe reports. Expanding into a market on a "de novo" basis — opening new branches instead of through an acquisition — is tough. Really tough. It's even harder in Massachusetts because of the competition posed by the state's healthy ecosystem of community banks, at least 100 of them. This vibrant scene of homegrown banks makes Massachusetts unique, particularly because most are mutual banks that aren't subject to the whims of the stock market, according to Samantha Kirby, co-chair of the Banking and Consumer Financial Services practice.