Changing the links and doing nothing else would be a pretty dumb MITM. You could do a more complex variant which is not so easy to spot (targeting specific networks, injecting malware whilst modifying the checksum)

The key property of SSL that is useful for tamper resistance is that it’s hard to do silently. A random ASN doing a hijack will cause an observable BGP event and theoretically preventable via RPKI. If your ISP or similar does it, you can still detect it with CT logs.

Even the issuance is a little better, because LE will test from multiple vantage points. This doesn’t protect against an ISP interception, but it’s better than no protection.