Boston has lost its financial services clout. Santander’s latest move is just another example.

Banco Santander executive chair Ana Botín wants to make her Spanish company one of the leading banks in the United States. Not Boston— even though her US headquarters is here, on State Street. As recently as 25 years ago, Boston punched above its weight in financial services, with powerhouse mutual fund managers at almost every corner, a top 10 retail bank in…