Sorry, it's hard to gauge how technically I should answer a question. If I don't make it technical then I feel like I'm not really being very accurate... I think it's an engineering trait, I notice my co-workers do this a lot too.
Sorry, I can't do l33t speak. So I'll have to try English.
There are 4 ways that chips break:
electromigration: metal atoms in a wire move around because lots of lots of electrons hit them. Move enough metal atoms and the wire will either short with another wire, or have a hole in it and stop working.
TDDB: the insulation material that separates two key parts of a transistor breaks down creating an electrical short - which breaks the transistor. In most cases, if any one of the hundreds of millions of transistors breaks, it will break the chip.
hot-e: a key parameter of the transistor called "Vt" (threshold voltage) shifts over time - which essentially slows the transistor down. If it slows down enough, then the chip will calculate an incorrect value.
BTI: Similar to hot-e but for a different type of transistors and happens for a different reason. Usually fixed in the factory.
In all but hot-e, increasing the temperature a little makes the chip a little more likely to break (this is all statistics... there is no "do this and this will kill your chip..." it's all a matter of probability). In hot-e, lowering the temperature makes it worse.
In all of these, increasing the voltage a small amount makes them much more likely to break the chip.
As to why 10% more voltage is much worse than 10% more temperature, well let's take the example of electromigration and look at it in detail.
Wires are made up of atoms all lined up. Electrons flow through these atoms. An electron is a very small thing, and atoms are a lot bigger. So the idea of an electron moving an atom around is a lot like someone trying to move a car (atom) by shooting a BB (electron) at it. Clearly to ever hope to move a car by shooting BB's at it, you would need a lot of BB's... a storm of BB's. But if you get enough, the car will move. Millions of BB's and that car will likely start getting pushed around. The temperature of the chip could be thought of as how slippery the road is. A little bit more slipperiness isn't going to help a BB move a car. It helps a little but not a lot. On the other hand, the voltage determines how many BB's you have, and it's not like 10% more voltage is 10% more BB's (electrons), you get a lot more than 10%. And worse than that, because increasing the voltage in a chip also increases the temperature (all things being equal, like same heatsink, same air temp, etc.), increasing the voltage is a double-whammy.
The others are similar... but more complex to explain (I'm still not sure that the experts really completely understand the low-level details of both TDDB and BTI...).