First off it is not clear this will succeed, it is early days still.
Your lining up issues was well done, since it highlights a number of important points.
I suspect most of the issues are economic and not so much technical. There are technical issues of course, but if the money is not there, it can't happen.
Launch Costs
Launch costs are way down, by virtue of new entrants in the market dropping costs. (SpaceX, but they are forcing their competitors to drop prices, new designs (ULA Vulcan, Ariane ADELINE, etc). The need to launch 600+ satellites also helps feed the launch market, and in fact last time around, the collapse of Teledesic knocked out some marginal launch providers who were counting on the launch rate to be profitable. With SpaceX planning Starlink with 4400 satellites, and possibly a VLEO 7000+ constellation, prices MUST go down. SpaceX is pushing their BFR for all launches, and that is designed for severly low launch costs.
Financial Backing
Microsoft at the time was one of the larger companies in the world, and very profitable. Today, Google dwarfs Microsoft of those days. Google has immense cash reserves and if they are willing to back this through thick and thin, have the money to do it. Microsoft in theory did back them, but the cost was a much larger proportion of their income compared to Google. (I don't have numbers, but Google has cash reserves I had heard on the order of 200 Billion. Microsoft never had that much.)
Core Market
The Internet in 1994 vs 2014 is very different. Google requires Internet to operate. Microsoft still sold software with or without the Internet access.
The belief at Google seems to be, mobile is the next market to win, and there are billions without access. If Google can provide that access, it gives them a leg up on getting those billions as new customers. (Be that in Android and hardware on the device side. Or Search, Voice, Mail, everything else to drive ad revenues on the software side).
Google has considered long duration solar powered drones, or balloons as relay stations for Internet access. Every aspect of their core business requires connected people. They want to connect everyone, and sometimes it seems like they take a 'no matter the cost' perspective.
Other Competitors
For fun, lets also consider the SpaceX constellation, now named Starlink. On the one hand, SpaceX do not have the financial backing Google can provide OneWeb (Even the $1 billion reported to be committed is a pittance on a constellation this size). On the other hand, SpaceX has the launch capabilities, and needs the launch rate to increase to get costs down for other customers, so is incentivized to get a constellation launched. Also, they own all excess capability on launches, and can resell it or use it for their own satellites. Thus the cost of starting Starlink for SpaceX is severely reduced. (Musk is reported to want to launch 2 test satellites to test design early (Scheduled for a Jan 2018 launch as a secondary payload on a paying customer.) But SpaceX's core market (Nor Tesla, nor Solar City, the trifecta of Musk's interests) is NOT Internet related per se, so it will be interesting to see if they can succeed.
