There were links posted on how things came to what they are. Apparently the disclosure was not quite planned, nor the donor countries' response expected - while the prevailing view among the IDF and other related professional bodies in Israel was that UNRWA's closure is something better left for post-war time. Seems like it was a combination of some information leak (under investigation), and then a snowball rolling - with politicians jumping on for the ride.
But for all that, it doesn't change the evidence, nor does it dispel the dramatic reaction.
Unlike you, I think it would not be that hard to replace UNRWA, post-war.