It was an afternoon when the West Ham support could not bear to watch. So many of them did not. Four-nil down in first-half stoppage time, their team as abject as Arsenal had been assured, there was a ­remarkable scene on the concourses outside the London Stadium – a knot of thousands of home fans, who did not appear in any rush to return.

Some of them did, trickling in as the second half got going and there was a point – after what had to have been a good deal of conscience‑searching – when the ground did not look too empty. That would change.

Related: Arsenal and Saka bring energy and noise to their renewed title challenge | Barney Ronay

It had to be Declan Rice. The former West Ham hero had set up goals with whipped dead-ball deliveries for William Saliba and Gabriel Magalhães – Nos 1 and 3, to be precise – when Ben White cut back and Leandro Trossard and Martin Ødegaard left it for each other. Enter Rice.

The midfielder’s shot from outside the area curled away from Alphonse Areola to find the far corner and that sound you heard were of seats clicking back and people making for the exits. Rice did not celebrate and when he was substituted immediately afterwards, there was generous applause from the West Ham fans who had stayed.

For Arsenal, it is four wins out of four since the winter break, this a result to back up the big one against Liverpool last weekend. It was the burying of a ghost, too, because it was in this game last season – a 2-2 draw from 2-0 up, Bukayo Saka missing a penalty at 2-1 – that the unravelling of their title challenge started.

The story, equally, was of West Ham’s humiliation – how, after Saka had made it 2-0 from the penalty spot, they subsided to such an extent that the TV cameras were picking out the club’s owner, David Sullivan, and wondering what he might do next with the manager, David Moyes.

West Ham beat Arsenal 2-0 at the Emirates Stadium on 28 December, a result that seems to have been lifted from another lifetime. They have not won since and if the final scoreline was horrendous – it is their joint- heaviest defeat in a home league game – then worse was the complete absence of fight, especially in defensive situations.

It was Arsenal’s joint-biggest margin of victory in an away league game and one short of their all-time mark – the 7-0 Cup Winners’ Cup ­victory at Standard Liège in 1993. They have been criticised for celebrating too lustily. There was never any danger of that, the jeopardy ­missing in action – like everybody in claret and blue.

Related: ‘I understand the fans leaving’ admits David Moyes after West Ham shocker

Arsenal were patient at first, ­laying the groundwork for their control. They did not panic when Trossard – playing as a false 9 – missed a header from Saka’s cross. He never looked like scoring. This is what happens when you lack a true No 9, it felt as though people might say. That plot line would be rather overtaken.

Ditto the one about Arsenal trying to score the perfect goal. They almost did when Ødegaard released Gabriel Martinelli with a lovely ball over the top. When he crossed low from the left, Ødegaard was close to reaching it, having not hung around to admire the pass. He did not quite get there. Same old Arsenal?

By then, Trossard had drawn a reflex save out of Areola with a banging volley from Martinelli’s cross but everything would change – sharply – when Rice curled in a corner from the inside left and Saliba was simply too strong for Edson Álvarez, too full of desire. Add set-piece delivery to Rice’s burgeoning armoury.

There was no secret about what Moyes wanted to do – remain compact, punch hard and fast on the counter. Yet his team could get nothing going. Their first-half performance was an abdication; it was no exaggeration to say that Arsenal could have been 7-0 up by the end of it.

They fell apart after the penalty, which was awarded when Saka fastened on to a long ball from Trossard, went round Areola, felt the contact and went down. Saka had blown a couple of chances – a free header from Jakub Kiwior’s cross, an overcooked dink after Ødegaard’s prod. What happened from the spot last season also must have been on his mind. He did not show it.

The home crowd had booed Rice at the outset, not with any real venom; more because it felt like something they probably ought to do. But the jeers upon the half-time whistle for Moyes and his players had feeling, all right.

West Ham had conceded the third when Rice sent in a free-kick and Gabriel, having stepped back from an offside position, timed his move forward for the header. It was Arsenal’s 16th set-piece goal of the season, excluding penalties – a league high. The fourth was even easier, West Ham’s resistance powder puff. Álvarez lost possession and then it was Kai Havertz to Ødegaard to Trossard, who came inside – under no pressure – to guide into the far corner.

The second half was nothing more than a contractual ­obligation. ­Trossard shot high and Saka was denied by Areola before the England winger exploded inside to drill one into the near corner. Then came Rice and the exodus. By full time, only the ­hardiest souls remained. “Thank you for your support, have a safe ­journey home,” the stadium announcer said, brusquely.