This is one of those things where there is a thin line between amazing progress and amazing failure. Musk has previously described the cash chasm that Starlink must past through before reaching profitability. For success he must get large revenue streams from Starlink, which requires large constellations of satellites. Nothing technically impossible about this, but getting it done before the cash runs out is a real problem. Apparently he was counting on Starship to get this constellation into place quickly and relatively economically. Again, doesn't appear to be technically impossible, but requires solving a great many problems in a hurry. Faster than anyone has solved them before. He has already done many of the things, but there are a lot to do. Some of which (regulatory issues for example) are not really anything he has a lot of control over.