Who is it that puts such huge effort into blaming them?

Obviously it's those who are to blame themselves, arch enemies of both Jews and catholics, and of the well being of humanity.

Who are they?

It's the freemasons, and yes some of them claim to be Jews, and some of them claim to be catholic, and the (roman) catholic church is heavily infected nowadays, but most jews and catholics seek righteousness and disgust their ways.

Compare what they are doing now with what they did in the french revolution.

I suggest you read Barruel's classic about that.

https://archive.org/details/BarruelMemoirsIllustratingTheHistoryOfJacobinism/

So who are the freemasons?

They may claim to be Jews, but they are from another congregation (or synagogue if you will) alltogether.

Their ways are canaanite not jewish.

They are Gibeonites if you ask me.

Deceivers descended from Canaan, son of his grandmother, himself.

Proud of their heritage, hence their incest.

Helped by deluded and by evil people of all kinds.

One example of these enemies and their ways are the two judges written about in the book of Daniel.

Those judges tried to enforce themselves upon the righteous Susan, and when unsuccessful tried to get her murdered.

All the elements are there, devious people acquiring positions of power and respect, collating, misusing their position to further evil and lies and quell good and truth, misusing their position to try to let righteous people do evil, misusing their position and take advantage of the harmless, sexual preoccupations, murder and using it to cover their tracks, and finally being uncovered as a descendent of Canaan instead of Judah.

Try to trace their cult, via manichaeism, hermeticism, kabalism, freemasonry, and extended with all kinds of heathenry.

Try to follow the money, Phoenicians, Carthagens, mediterranean pirates, Venetians (the ones who sacked Constantinople), …, Antwerp, Amsterdam,  London, New York.

Try to trace their symbols, eg the Cathar village of Minerve in France (see https://en.m.wikipedia.org/wiki/Simon_de_Montfort,_5th_Earl_of_Leicester).

Try to trace their aims, veganism (outside cannibalism), putting evil on an equal footing with good, sexual perversions, human sacrifice and consumption of blood, putting acclaimed knowledge above morality.

And about this blood libel: it's very likely that some of these accusations are true and no fairy tales. That is, people  who where known as Jews indeed committed these atrocities. But again, altough they may have claimed to be Jews, they belong to a completely different congregation. Their actions are utterly alian to the Jews.