Are satellite links easier to take down than a fiber link? No

Depends on what we're talking about.

Is it easy, in any conceivable scenario, to take out an entire nation's web of cabled infra? No, not at all, and would require the same state actor level threat it would to take out a satellite train. It's just cheaper to do it in space, and less prone to failing than it would be to try a land-based infra attack.

Do Starlink satellite need to be replaced at extreme cost? Yes, but so does terresrrial network infrastructure.

We do not need to replace all the fiber, and all the coax, and all the transceivers every 5 years, at a cost of 10s of billions. At most? You need to replace stuff in a DC/DSLAM/termination point and the client side. All the fiber and coax in between is still usable for 20 years, even. And the endpoints don't need to be upgraded physically, most times, it's a software update pushed.

Ever wonder why Ukraine was using Starlink for network connections in the first place?

Because Russia bombed their power plants, all the cabling, and it was a literal war zone. And relied on infrastructure that was terrestrial outside of the war zone. And to replace all the infra (Outside of the power plants) will still be cheaper than a couple of trains being launched for StarLink.

Your points, that satellites based networks are more vulnerable and prohibitively expensive is simply not compatible with reality.

You do know StarLink can be taken down by targeting their ground stations, right?