We had the same dilemma after we watched it.
I also had a really hard time, after watching so much of them in the house, with them not covering the conversation where he'd told her the children had been in the house. Maxine only admits to that when she was going through the court process. Why didn't they do a drama re-enactment of that?
I guess the point of the drama was to show how we'll probably never know.
I think, personally, that he never told her what he'd done. I think he denied it and I think deep down she knew but she also didn't believe it, if that makes sense?
I had an ex who used to do drugs. I had absolutely no idea. There had been some weird behaviour, but every explanation he gave for it, i believed. One night he was 'in the shower' and he was taking ages. I started knocking on the door. He came out, dry hair, dry feet - and I said I thought you were in the shower and he said, I was. He walked past me and drug paraphernalia fell on the floor, from underneath the towel he had wrapped round him. I said, is this for drugs? And he said, 'no. well yeah I confiscated it from a lad at work.'
I remember being confused and thinking it was strange but, ultimately, 24yrs old me believed every word that came out of his mouth - despite everything in that situation being glaringly obvious it was bullshit. It was obvious he hadn't been in the shower and he literally had drugs falling out from under his towel. But still he told me it wasn't so and I believed him. I was just incredibly gullible and naive and also I couldn't square my lovely boyfriend as being someone who snuck into the bathroom to take class A drugs. So what he said had to be true.
So that's kinda how I think it was for Maxine. The stakes, of course, were so much higher and so much worse but I think that probably made it easier for her to believe him - the crime was so horrific that in her mind he couldnt possibly have done it. When you're in love with someone - it's hard to see that person as also a person who kills innocent little children. Even if, it's glaringly obvious to everyone else.