I imagine the concern becomes survivability. Israeli's really like their multiple levels of backups, and having a data copy out of the reach of enemy arms seems high priority.
Iran attacking US-East-1 would certainly be unusual.
They could likely work around that, multiple locations in-country and an off site encrypted backup out of country.
More likely is it was "aid" from the US which usually comes with stipulations about what/where they can spend it - common with weapons/military kit, wouldn't be surprised if they did something similar with cloud services.
Iran attacking US-East-1 would certainly be unusual.