What does this tell you then? All the "he picks Robinson because he's his favourite and pashun" is obviously BS given he picked Souttar over him.
Perhaps Holding isn't very good? I know this is impossible for people to consider, but it might be true.
Some of this has been covered already, but I'll chuck my two bob in - it is a forum after all.
It feels somewhat like comparing apples and oranges here. Souttar was signed before the season started. He didn't make a league start until Norwich away on August 24th. Between then, and suffering his injury on Boxing Day, he missed one game (West Brom away, because of his red card vs Sunderland). That's 20 starts, plus a sub appearance vs QPR at home. Of those games, Souttar and Anel started 13 games together. Of those 13, we kept a clean sheet in 8 of them. In an admittedly small sample size, that's a 61.54% clean sheet ratio. Once Wilder had that partnership up and running, it was practically impossible to try and justify breaking it up, because they were so incredibly effective together.
In the 6 games where Robinson stepped in to play with Souttar, we kept 6 clean sheets. I'd argue that based on the degree of success both players enjoyed playing alongside Souttar, that they each were not the key factor in the success of the partnership. As someone else has already mentioned in the thread, the presence of Souttar was a metaphorical "crutch" for both Anel and Robinson - Souttar was such the stronger player, that he caused the other to perform better.
The question then becomes one of why Holding was not allowed the opportunity to do the same? Yes he wasn't fit when he came in, but in 19 matches he was available for us to select him, he made only 4 starts:
1 - Bristol C (H) - subbed off on 77 minutes while 1-0 up. Equaliser conceded after he left the pitch.
2 - Cardiff (H) - clean sheet (2-0 win)
3 - Stoke (A) - clean sheet (2-0 win)
4 - Blackburn (H) - 1-1 draw. Blackburn had to press to try and get in the playoffs, while we had had 3rd place tied up for several weeks. Still looked pretty comfortable.
All the other appearances he made, according to transfermarkt, account for just 77 minutes of football.
The issue at hand is that our central defensive partnership, once Souttar got injured, looked incredibly frail. We became far weaker as a unit without his presence in the defence, and teams looked to take advantage of that a lot more often as a result. Holding came in having a wealth of experience at Premier League level, being comfortable in possession, even when pressured by opposing forwards, and we chose not to utilise that option?
Rather than targeting Robinson, I'll address the CB partnership as a whole. The pairing of Anel-Robinson has, on occasion this season, looked distressingly frail. Neither player was capable/willing to fill the void created by Souttar's departure, and so we were much more easy to exploit as a result.
I can concede, as you have asserted already, that I do not have the luxury of watching the players in training every day. That I do not get as comprehensive an understanding of them as the manager and coaching staff. But I do get to see them on the pitch, week in, week out. And it doesn't take a coaching licence to see that we had the option of a man who has been a Premier League player for almost 10 years, who has won the FA Cup twice, who clearly knows how to operate at a high-quality, high-pressure level, and instead trust a pairing that has often had signs of a rick in it.