Bank of America paid more because despite it all ML fits well with its financial services empire
BOA was willing to pay a premium because it's betting that in the long term the resources and services it acquires with ML, namely the brokerage business, wealth management, asset advisory, are worth the short/mid term headaches that come with it...
Also, even after the 70 percent premium BOA paid, the ML stock is still valued at only about 1/4 of what it was a year ago, so BOA may still view it as a good deal.