I'm trained in forest management, so I hope this answer will suffice. Trump is partially right when he talks about how fire prevention is shit. The main agencies that manage wilderness were explicitly trained to let things grow unabated in a lot of instances to the point of being powder kegs (think Smoky the Bear). There was no maintenance (eg: controlled burns and brush control) in a ton of areas. Normally things would grow, burn through natural methods, or get maintained by wildlife eating things (or other means). Human interference also altered natural preventions of massive fires. This became a huge issue when humans decided they wanted to build houses and infrastructure directly in or around forested areas.

Of course this all falls apart when you realize the whole argument is obviously in bad faith and that the factors involved in climate change far outpace anything the NPS or FS is responsible for. Every federal land management agency does need systemic change regardless (especially the Forest Service, since they explicitly exist to serve commerce logging and mining). I didn't watch the debate, I'm just going off his twitter comments.

Read "A Walk in the Woods" by Bill Bryson if you want to learn how incompetent the land management agencies are.