Hypothetical question because it wasn't. However if it had been a clean tackle it wouldn't even have been a yellow so the question doesn't arise.
But your reasoning for him being sent off is because of what happened after his challenge. So, if that is the case, even if his challenge was good, because after the challenge Gomes still broke his leg, he should've been sent off.
Bookings are meant to be a punishment for the challenge itself, not the aftermath.
Regardless of all this, hopefully Gomes makes a recovery and is playing football again as soon as possible.