As far as I know there is no tantalum capacitors inside IMSAI 8080... :confused:
Only aluminum electrolytic capacitors were used.
Unless someone did an extensive upgrade.
...maybe you've only seen empty ones?
Not a heck of a lot of anything in just the case. (and no, it wasn't one of the giant power supply capacitors that exploded.)
Start adding an assortment of some of the hundreds of various boards to make the system run, however, and you're bound to run across some tantalum capacitors.

I believe the one that blew up in mine was on a memory board.