I wanted to expand on what jobowi5588 said.

To be clear: what FL's lover had noticed was merely that she had been carrying around a book in her work bag that she was not reading, and told her that she could take the two hours of delay to read that. Seems like something that he would be in a much better position than her husband to notice (I mean, it's a very different situation, but it reminds me of the families and friends of people that commit suicide, where even the people closer to them might not notice something was wrong, and it doesn't have to be for lack of care), given he worked with her and saw the bag, saw how she was at work, and is an external person, and sometimes it's easier for someone from outside/not involved to notice some things that you yourself, or those closer to you, miss.

Point being, it's not as if the guy had mind powers either, he just happened to be in a time and place where he noticed she was busy with work and not progressing on the book, which, given he saw her at work and carrying her work bag with the book around, he would have been in a suitable position to notice. Again, this was more the trigger for her to realize stuff like the fact she couldn't get two hours to read the book, and the whole thing with the kids, etc. that her lover didn't have any clue about (because it's not as if he has special powers and knows how to read minds, either), so it was more of a chance for self realization.

And, again, it would make absolutely no sense for her to expect her husband to notice something she didn't notice herself, and in general to know something she had not even known herself if she didn't tell him. He might just happen to end up in a situation where he happens to notice something she had missed, like her lover did, but that's something of a hit and miss chance: that's not something that is reasonable to count on in terms of communication in a relationship, you need to actually communicate and tell your partner things. They are not with you at work, they are busy themselves, and they are not present at work and might not be present when you do other things, for example with the kid and moms, so they might never end up in a position where they would even have the chance to notice something like the book thing (it's not as if they would rummage through your bag).

Bottom line, people are not mind readers, people not involved in a situation might have an easier time, or have the chance to, notice things that you don't notice yourself and that even the people closer to you miss, and it doesn't mean they care about you more than you care about yourself or that those around you care about you, they simply happened to notice something from the outside that you or the people around you missed, and you yourself are the one to know that it's a symptom of something greater.

And, all in all, it's unreasonable to expect the people in your life to just know, if you are not going to tell them. They might not have had a chance to notice, they might have their own issues to deal with, etc. It doesn't mean they don't care and that they wouldn't care if you told them and they knew, obviously. Especially if you yourself didn't notice, and you were in the perfect position to because you had complete information: how could you just expect someone to notice something you didn't even notice yourself? They might by accident, by chance, but it's obviously not something you should rely on as a strategy, and just wait around. I mean, if you didn't notice yourself when you knew every part of the story, the expectation that they would seems unreasonable.

But even if you noticed and they didn't, communication means that you need to tell them, not that you need to wait for them to figure it out as if they were Sherlock Holmes. If you don't talk about a problem and just expect people to notice and solve it, then you are setting yourself up for failure. There might be millions of reasons why they might not take notice, and they don't have to be a lack of care or interest in your well-being: obviously ML loved his wife and would have gladly helped had he known she was struggling, but she didn't notice the issue herself, and when she did she was uncommunicative and even lied about it, acting as if it was all okay (even when he asked, and proposed they took time to reconnect), and he believed her.