How has the word epicurean come to mean excess?

Quote from ThinkingCat

could anyone briefly summarise why Christianity was a problem for Epicurus

Early Christians could not reconcile the two traditions, and Roman Epicureanism was an ideological competitor to Christian evangelism. "Also some Epicurean and Stoic philosophers debated with him. Some said, 'What does this pretentious babbler want to say?' Others said, 'He seems to be a proclaimer of foreign divinities.' (This was because he was telling the good news about Jesus and the resurrection.)" (Acts 17:18 NRSVUE). Whereas elements of Stoicism were incorporated into Christian theology (Providence, a Universal God, etc.), Epicureanism is antithetical to Christianity.

The image I shared above Pre-Christian Philosophers and Pathfinders of the Way is a contemporary work based on the frescos at the Holy Monastery of Vatopaidi on Mount Athos in the style of Orthodox iconography. The Christian artist depicts Socrates, Plato, Aristotle, Pythagoras, Homer, and others right alongside St. Paul and Justin Martyr. Many Christian theologians (such as Justin Martyr) have proposed that Plato (for example) went to the Kingdom of Heaven, and apologized for his heresy as a consequence of being born prior to Christ's ministry. Not so for Epicurus.

In a similar vein as what Nate just posted that the Christians would have held the Epicureans in particularly low regard there is this from Alexander the Oracle Monger, where again the other schools were willing to collaborate with the revealed religionists, but the Epicureans were not:

The prosperity of the oracle is perhaps not so wonderful, when one learns what sensible, intelligent questions were in fashion with its votaries. Well, it was war to the knife between him and Epicurus, and no wonder. What fitter enemy for a charlatan who patronized miracles and hated truth, than the thinker who had grasped the nature of things and was in solitary possession of that truth? As for the Platonists, Stoics, Pythagoreans, they were his good friends; he had no quarrel with them. But the unmitigated Epicurus, as he used to call him, could not but be hateful to him, treating all such pretensions as absurd and puerile.

Epicurus.info : E-Texts : Alexander the Oracle Monger