Actually, that’s more of a misconception. We’ve literally had four decades of electronics miniaturization since then.
Are you really going to argue that since ENIAC took up a whole room, it must have had boatloads of computing power? By modern standards, it’s way less powerful than a Raspberry Pi.
Also, we haven’t just increased miniaturization, but all 30 of the CPUs for the original Deep Blue ran at 233mhz.
That phone is likely a quad-core CPU (which means technically four CPUs) all running at 1.5+ gigahertz.
So is it really that surprising it can now do stuff Deep Blue did with a fraction of the CPU cycles?