Prospective acquirers will often pursue potential targets simultaneously and, if they go silent on you, this may have little or nothing to do with whether you followed up diligently or not. In my experience, when an acquiring company wants to move, they know how to do so quickly, at least to engage in sufficient due diligence to see whether they might want to do the deal. Thus, when you do get in a situation where you are getting slow or evasive responses after an initial expression of interest, or where things go silent after an initial set of exchanges, I am not sure there is much you can practically do about it unless you have options to sell to others and use this as a lever to speed the process. You can be as aggressive as you like in such cases but, if the acquirer is simply trying to keep options open, you won't be able to force things absent a credible threat of going elsewhere.

That said, this one may have simply fallen through the cracks owing to the early failures to follow up more aggressively. Only the Google people can know for sure.