The other factor is the buyer probably looked around at competitors and noticed there was another business less valued that they could pump the same capital into and outgrow this business.
https://m.youtube.com/watch?v=JlwwVuSUUfc
https://www.quora.com/Silicon-Valley-Season-2-Episode-2-Runa...
Older incumbent companies, especially, may have giant 'business development' teams who almost recreationally do deep x-rays of emerging threats/opportunities. All their staffing/trips/flirtatious-discussions/legally-drafted-non-binding-letters-of-intent may be a rounding error in their bottom line, a cheap research expense. They can go through all the motions of an acquisition, appearing serious to the hopeful founders, with a negligible interest in actually completing the deal.
I mean sure, they'd bite if they saw a can't-lose bonanza - their talks are panning for gold in your stream, before buying or even renting your land. Even if 99/100 envisioned deals eventually fall-through, they're just happy to learn all the proprietary business internals.
See also: ~pg's 'Don't Talk To Corp Dev': http://www.paulgraham.com/corpdev.html
"When a sufficiently high-up decision maker decides he/she wants to buy your startup, he/she will attempt to meet with you constantly and put time pressure on you, so as to prevent you from shopping the deal and getting a better offer. The absence of this behavior indicates the other company is not serious about acquiring your business."
One counter I would make to PG's essay is: investors, whether accelerators, VCS, or otherwise, predominantly benefit from big exits... and so they have that effect of pushing towards polarized outcomes ($0 or big). But "small" exits can still be very meaningful for founders.