My own memory of the events (which might be very wrong) was that a new vice-president of IBM semiconductors decided to drop bulk CMOS and focus exclusively on SOI (Silicon On Insulator). That suddenly left Transmeta without chips to sell. They had to scramble to find a new supplier and design their next generation processor for it (since the Crusoe wasn't portable to any other fabs). They were able to launch their Efficeon on TSMC 130nm (with a later version on Fujitsu 90nm) but the gap in supply was far worse for a startup than it would have been for a big company.
Backwards. The incompetent Transmeta board picked a VP from NVIDIA to be the CEO and his first action was to kill the IBM contract and move to TSMC, and forced TSMC to use a new unqualified process. This left us without chips to sell for over a year and notebook venders were furious and never returned.
This is what killed Transmeta, not all the technical details.
Cisco and Cray used IBM fabs for multiple generations in the aughts but they weren't startups. Before the rise of TSMC it was a weird situation where fabless companies were kind of picking up extra capacity from IDMs.
I'm curious: Is there a consensus on which startup companies achieved success using IBM as a fab? or if not a consensus, I'd settle for anecdotes too.
My own company (which built 40G optical transponders) used them back in that era. While the tech was first rate, the pricing was something to behold.