At WrestleMania, Drew McIntyre made history when he became the first British wrestler to win the WWE Championship. However, in the weeks leading up to his win over Brock Lesnsar, there was no sign of McIntyre on RAW, something which definitely lessened the impact of the build to their match at the Show of Shows.
In the latest Wrestling Observer Newsletter, Dave Meltzer explained that on March 12th, both McIntyre and Sheamus were both forced to leave the UK early. They were in the country to promote WrestleMania, but when travel restrictions started being put in place because of the COVID-19 pandemic, they both returned to the United States.
As a result, they had to self-quarantine, and that's reportedly why McIntyre missed the tapings leading up to the Showcase of the Immortals.
He did appear on the March 23rd episode in a pre-recorded backstage promo, but we never got to see him get physical with The Beast, and Paul Heyman instead delivered the typical promos leading up to the PPV . This is the same reason Bobby Lashley and Kairi Sane were nowhere to be seen.
It all worked out in the end, of course, as McIntyre both won and defended the title on the same night at WrestleMania.