Fusible link failure Toyota Hilux 1990

I have a 1990 Hilux diesel truck and recently the alternator started
intermittently failing, probably the brushes.  The garage recommended
replacing it but had problems installing it as it had an internal
voltage regulator whereas the old one had an external.  Consequently
they got an auto electrician to do the installation.

Subsequently on a long journey at relatively high speed at night the
lights suddenly went bright.  Being naive I thought "Oh good I can see
better" but about 20 minutes later there was a loud bang and much
rattling.  So I stopped.

It turned out that the fusible link had blown causing the wipers to
operate (the rattling) but much additional damage was done including
blowing the regulator, the tacho, all parking lights, the dashboard
illuminator and the immobiliser as well as stripping the splines on the
wipers.

The auto electrician at the place I am staying was very good and
replaced the regulator under its warrantee but I still have to get the
other damage repaired.

I have three questions:

1) What could have caused the fusible link to blow?

2) Having replaced the link but not knowing the cause of the failure is
it likely to occur again?

3) Do I have a reasonable claim on the garage that fitted the new
alternator?

I would very much appreciate any advice you can give me

Thanks

Jeremy