It does appear that he tried to comply. But he also received multiple, contradictory orders in the middle of an incredibly high-stress situation (sibling comments have talked about that aspect, so I'll refrain). From every cop I've talked to, and I have a few friends as well as relatives, an officer's training is supposed to emphasize the need for clarity and precision in giving a suspect orders. Especially at gunpoint. Any confusion increases the danger for everyone involved.

At one point in the video, Shaver was down on the ground with his fingers interlaced behind his head and in plain view (~13:45). In that position, his hands are far enough away from pockets and waistbands that any attempt to retrieve a weapon will be clearly noticeable. Not to mention extremely difficult for him while laying prone; to reach his waistband, he'd have to release his fingers and reposition his entire arm with his hand moving along a semi-circle path that's generally going to be pretty wide unless you're talking about something with pretty extreme flexibility (even then, your shoulder blade is going to jump up noticeably.

Shaver was compliant, and not in a position to easily threaten the officers. They had him in a perfect position for two officers to move forward, with one cuffing him/searching him while the other maintains watch with his weapon out. Instead, Officer Brailsford ordered Shaver to release his fingers, push himself up to a kneeling position, and literally start crawling (~16:25). This involved additional orders, some of which further contradicted the ones that literally came immediately before them and all of which contradicted the original ones Shaver was in compliance with.

Worse yet, forcing Shaver to crawl ensured that one of his hands would wind up being close to his waistband as he moved forward. The one thing that they wanted to avoid in the first place. There's no way not to; it's how you maintain balance while crawling and is basically automatic. That's part of why forcing a suspect to crawl isn't (as far as I'm aware) part of any police procedure. It partially obscures at least one hand while crawling, the motions involved are similar to those that would be made if a suspect were pulling out a weapon to threaten you with, and the act of crawling is awkward as hell for the suspect. And when human bodies experience awkward movements, our reflexes react. In this case, it got Shaver shot.

Those same issues also probably stressed the hell out of the other officers as well, as they now had to start judging each movement in the crawl.

Giving them a very big benefit of the doubt, Officer Brailsford presumably wanted to get him away from the open doorway so he and the others wouldn't be exposed to anyone in the room. But they could have accomplished that by having Shaver stretching his hands out in front of him while on the ground, and having three officers advance forward. Two could literally drag him out of the way with one hand each while the other covered the doorway with a weapon.

tl;dr - Brailsford had Shaver in a perfect position that greatly minimized risk to himself and the other officers. He ordered Shaver to leave that position, and in a way that increased their own risks and the tension in the hallway while making it more likely that Shaver would make a mistake while trying to comply with the contradictory orders.