Ole just got extended for three years, you need to take that into account, from the executives point of view sacking someone a couple a month after a 3 years extension is quick, it's very quick and costly. And since there is no obvious candidate available, that decision is particularly difficult to take since no currently available candidate gives you any indication that he is better than the current managers above us, Conte was on paper the best option but it's not there anymore.
I'm not suggesting that keeping him is the right move, I'm simply highlighting the fact that it's not an obvious or easy decision. Unless things become toxic it makes sense that the board would give Ole as mush rope as they can, now the alternative would be if for example someone like Zidane or ten hag make themselves available immediately.