According to what data? Are European companies returning better on average? Until shown otherwise I'm not even certain American tech is performing better (outside the big 5, but we're talking startups).
As for Intel: new 25B investment (!) into Israel is coming https://www.reuters.com/technology/intel-get-32-billion-gove... I'll be surprised if the other big ones are about to leave.
Don't get me wrong, Israeli startups are hurt for sure, many will have to shut down (as is happening all over the world), but many others will take their place - if not this year than the next. (A.I, defense, cyber, Israel still has tons of manpower capable to compete in those fields)