Earlier quoted context omitted.
However, if the merging companies compete in the same market, it would be fairer to claim that "It's like taking the number two and number three sprinters in the world, and having them run IN SERIES against the number one sprinter." (emphasis mine). Because number two and three companies merging to a new number one does in fact happen. (Note that this is the case here, though. No idea where Google is going with this.…
I don't know that that analogy follows, because agglomerations of thousands of people doing a complex task really aren't that comparable to two people doing one simple task. Taking one example I know of second-hand: My brother worked for the #2 company in his industry at the time they acquired #3 in an effort to overtake the market leader. It worked out disastrously. It turns out that #3, despite being the less profi…
I mean, it could have been that simple: #2 could have just entirely liquidated #3 and taken over their brands, marques, and physical assets like buildings, without retaining a single employee or officer of #3; or if they did keep the employees, it would just be by putting them into an "internal talent pool" where they're being paid to do nothing for a month or two, while they get filtered through #2's HR department as if they were new hires, either being placed in #2's structure or dropped.
This would mean that #3 would be essentially erased from the marketplace at the moment of acquisition: no further revenues, but no costs either, all creditors paid off by #2, etc. #2, however, would also immediately be free of the effects of #3's competition on their bottom line, which might balance out that lack of #3-revenue for them quite well. Many customers previously using #3 would find that they had simply stopped communicating or delivering on their promises for a period—and if they were going to switch allegiances based on that, who better to switch to than their still-business-as-usual acquirer, #2?
And, of course, presuming #2 already had logistics pipelines feeding the same markets as #3, and produced essentially-indistinguishable products from #3, it wouldn't take long to just start producing #2 products with #3 brands slapped on them and start sending them to their new base of #3 customers, to return things to normal. (But in the mean time, they'd have already received many of those customers as switchers to #2, without having to "fool" them with the #3 brand.)
I believe this is the strategy employed by one of the big successful examples of M&A: Anheuser-Busch InBev. When the beer giant acquires another brewer, they don't keep them making beer; they just tear them apart, throw the acquired company away, and suddenly customers of MomNPop Beer Co. are drinking AB InBev beer in a MomNPop can. (They don't even keep the MomNPop brewery itself; there are economies of scale that make operating a bunch of small breweries silly compared to operating one huge megabrewery. They just strip it, sell the equipment for scrap—because otherwise they'd be encouraging someone to start another competitor!—and then sell or rent out the land, if owned.)