The show was always going to try to get as high a body count with recognisable characters as it could while holding back on eliminating any main players. So, that means supporting characters like Beric, who is more popular to book readers anyway, was likely to die in the invasion from the get-go. Without Thoros of Myr to bring him back from the dead as usual, he succumbs from multiple stab wounds sustained from saving Arya from a horde of wights running through the halls of Winterfell.