#1 What was the meaning behind Heath Slater's return?

One of the big moments of RAW happened at the very start when Drew McIntyre asked Dolph Ziggler what stipulation he had chosen at Extreme Rules 2020 for their WWE Championship match. The recently-transferred RAW Superstar brought out Heath Slater - a Superstar who was recently released by WWE.
This led to an intense segment where Slater accused Drew McIntyre of not being there for him when he was fired. Slater claimed that he called McIntyre every day after he got fired in 2014 and the two would end up having a match.
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Drew McIntyre ended his 3MB teammate's run with a Claymore Kick and after Dolph Ziggler berated Slater, Drew McIntyre came in for the save before embracing Heath Slater in an emotional moment. The 3MB sign indicated that they were missing Jinder Mahal.
But it was intense in every way and from the look of things, that's truly the end of Heath Slater's run with WWE on RA. We can't ever rule him coming back but in his mind, he seems to have accepted that it was over.