They didn't exactly build a terminal, they upgraded an existing jetty to allow a floating terminal to dock and connect to the gas network on the main land. Engineering-wise it was a fairly straightforward job.
This was a large project and completing it on time in 9 months is laudable.
A big fire can be bad, but is nothing like a detonation.
Germany already operates about 40,000 km of natural gas pipeline. This was a 26km extension in a flat and rural/industrial area. There was no engineering challenge here that they hadn't already pulled off hundreds of times before.
Doing anything like that in nine months is impressive. I haven't the faintest idea why anybody would say otherwise.