US level anti-trust laws don't touch on a lot of anti-competitive behavior, mostly specifically it almost solely concerns just trusts and monopolies. I don't think I've heard of a court case ever before simply on the death of a product.

But also US anti-trust laws at the federal level have always relied on a strong FCC, FTC, and US Attorney General's Office to execute, all of which are currently neutered and/or understaffed under the current administration (and may take years to recover even in the best case scenarios). The US has decided it is a season for trusts and monopolies.

(See the mergers of Paramount and WB into Skydance consolidating 200+ combined years of movie history into a single monopoly under the Oracle nepobaby and almost directly undoing/mocking one of the largest and oldest anti-trust cases which was US v. Paramount Studios which set precedents for how large a movie studio could grow that lasted almost 100 years.)

(There might be something the state of California could do, but I don't know how much they want to get involved.)

Do you think Deno was real competition for Cloudflare, and now that they've merged we don't have alternative options for goods/services that are mostly essential?

I think if Cloudflare and Google merged, it still wouldn't be a monopoly because of AWS (and many others).

I'm not sure if it is legal or not, but it happens all the time, and nothing is done about it.

IMHO, it shouldn't be allowed.

In what sense did deno compete with cloudflare? It is a niche runtime and cloudflare is a cloud platform