There was no upside because a) he had no defence for his crimes b) he would commit perjury on the stand
So no one thought Trump would testify, despite in the past him saying he would never 'take the 5th' because only guilty people 'take the 5th". Guess what? Trump was actually right, guilty people do 'take the 5th'. Guilty people like Trump 'took the 5th'
