This is kinda wanked, you're right that the whole Spectral Realm was collapsing but aside from it everything's exaggerated.
First is the size of that place, you only got proof of it being interstellar, fortunately I don't have to explain why this to you nor debate it, we have a page called Universe that sets up standards and if you disagree with it you need to make your own thread about said page. You also kinda talked like Mojo Jojo when explaining why it's universal in size, so note that's unneeded.
The collapse was a side effect akin to taking pieces from a building over long periods of time and then that building collapsing. Don't take the example literally but what I meant by it, the Spectral Realm had energies in it, that guy was syphoning them over long periods of time, this started to threaten everything, then the place started to not holding up very well and later it would collapse. It blowing up like a bomb isn't the standard assumption, it's Environmental Destruction. It doesn't change things how this would reach the main world.
For the same reasons, the guy having a machine to survive it doesn't scale to the whole tier that would have, like surviving something collapsing around you isn't the same as a bomb blowing it up in your face.
We're never told that this would destroy the universe too, just "the rest of the world" and "everything else as well", which can be anything like just the solar system or less.
None of his machines scale to the Environmental Destruction it can make
- Using the building example again, if "removing" all the parts of a building at once makes you Building level then removing some parts of it over time to make it fall makes you way below Building level.
- That energy in turn was distributed to his robots, making it even more unquantifiable.
- The place was also yet to collapse as the battle went, making it even more unquantifiable.
- Powering robots=/=they having the same AP as what's powering them, even if the final boss is the most powerful one (which it logically would) that doesn't necessarily mean much. The energy that powers them can just primarily serve the purpose to make them function while making their AP and Dura pretty high but to an unquantifiable level.
- Imagine I was some 10-C guy who used some hax to absorb a whole city & make it gone, I got that energy for myself, and used that power to blast another city and destroy it. That was City level. But I'm not City level anymore unless stated, I pretty much used 1 city to destroy another, I didn't absorb a power source that's always giving City level levels of power. Here even if the villain were to absorb the whole realm at once and if we knew he could use it at will to make 4-A attacks we could need to distribute that to everything he already used and powered with it. We know far less than those ifs, making it all even more unquantifiable.
The Syphons absorbing energies from the realm is a very specific gimmick they have and were doing from a long time, it would have been only attack speed if legit. But it has little reasons to be so, we have no idea the mechanics they do for their job, they may just take energy around, then more energies takes its place akin to gravity/because it's something the whole realm needs, and then the process may go on for a while, the realm and how its energies work doing most of the speed, we also don't know how much energy was being taken at a time.