Looks like a bad mix of mountains and a lot of flat ground - at least in Taiwan the water runs back into the sea pretty quickly

According to wikipedia, it reached a peak intensity of out to sea around 200kph sustained winds with gusts up to 280k which would make it a Cat 3 - 4? Also it's a big-arsed storm in sheer size terms. Down to 160 k when it made landfall but still caused a storm surge of 4.4m. Dropped up to 600mm of rain in the worst hit area.

"Idai was the tenth named storm and record-breaking seventh intense tropical cyclone of the 2018–19 South-West Indian Ocean cyclone season"

https://en.wikipedia.org/wiki/Cyclone_Idai