Two comments IMHO:
- Would you have said yes and looked into the details of their offer, you would have realized that the $12M are not upfront. Through retention packages and revesting, most of the price is typically paid over 3 or 4 years. So the offer was probably less attractive than it initially looks.
- $12M is never a good outcome for investors (at least big angels and VCs). They make their returns only on big exits.