Where's the standalone value?
Browsers have come and gone over the years, so the value of Chrome is not the most solid thing. It has obvious value *to Google* as part of their portfolio but does it have that value by itself?
Is it the engine? 'Cos that isn't the same thing; there are *lots* of browsers based on the same core, so it's hardly a special sauce.
Or is it the popularity? 'Cos how much of that is down to the product, and how much is just down to it *currently* being the default bundled browser on so many devices? Any reason for that to persist post-sale?
Or is it just the data? What is that actually worth when detached from the rest of the Google empire? What can a third party do to monetise just that bit, vs what all the other browser vendors can do too?
It might be the big dominant beast right now but once split off it could get overtaken by something else in exactly the same way predecessors did over the years. Assuming anyone still thinks supplying a browser is a worthwhile end in itself.
So maybe $50 billion is a bit much to ask for just another free browser in a crowded market not exactly flush with massive returns.