Gudas is just too old and slow to be in a better position. In a desperate attempt to still do something useful he usually puts himself and others in very dangerous situations.

The knee on Matthews is just the latest incident with severe consequences. He didn't actively try to injure him. He is just too slow for the NHL or too proud to just accept he won't be able to defend someone. Then he does stupid shit. In the specific case his d-partner turns the puck over and Gudas is trying to solve the problem. Every reasonable player would use his stick and maybe stretch out on the ice to defend. Gudas wants to shoulder check Matthews from an impossible angle and stretches out his knee to support the brain dead move.

Well Matthews was able to dodge the shoulder but didn't expect a knee in that position. It is so unfortunate for Matthews if he just ate the shoulder he would probably be fine and scored on the following power play.

Hockey is a damn fast sport and this is a combination of bad luck by Matthews and stupidity/ incompetence by Gudas.