Large icebergs may take 1000s of years to melt. So much of their mass is trapped inside, there's not enough surface area for heat transfer, they melt a tiny bit at a time.
Big companies are similar, trapping so much of their value under the surface. It's a wonder that more giant companies (I'm looking at you, Microsoft…) don't break themselves into smaller pieces, providing more surface area for innovation, customer interaction, brand extensions, etc. Less controller heat release, for sure, but much larger volumes, much faster, more to the pace of what consumers expect today.
Microsoft (and to be fair, others) have a thick outer shell, and it's preventing them from deriving huge value from their great research work, bright employees, and intellectual property. It's all trapped in a giant iceberg of process, politics, and bureaucracy.