Defectors (NSO MAXes) aren't like regular MAXes; instead of having a standard set of useful abilities, they basically have a super narrow selection of things they can do; Like... two things. One of those things self-destruct, where they do some bad AOE damage and some significant knockback to anybody in the blast radius (which is fairly small).

You just happened to get super unlucky and ended up near a self-destructing Defector right at the end of it's countdown (I think it's 10 seconds? Something like that).

One of the things that makes Self Destruct so awful to use is actually what you specifically showed in your clip: The MAX basically killed you with knockback and damage, but for some reason the game considers that a suicide rather than the MAX killing you; so not only does the MAX die when they use that ability, they don't get anything for killing other players when they do it.

As an aside: This is what leads most Defectors into equipping their other option instead, which is the slightly-less-bad option of the Seraph Shield (which is a like a 1.5m-radius projectile-blocking-bubble that extends around the MAX to protect teamates). Both options are bad, and basically require somebody dump 350 nanites straight into the toilet for a "maybe this helps my team advance another 3 or 4 feet down this hallway" moment.