Actually, it makes sense that it splits that way at Ocarina if you accept the general rules of time travel that writers over the years have established. When you go back in time to change things, you create a new timeline, so splitting it three ways there is logical according to those rules. That explains why there are three splits, and also why Ocarina is where it splits, being as focused on time travel as it is (though you'd then have to look at Oracle of Ages more closely).
Oracle of Ages though has Link defeating the villain of that game, Veran, in the past and then returning to the present. Since Veran was from the present and went back in time, killing her in the past kills her for good since she no longer exist in the present time because she left the present for the past.
Unlike Ocarina of Time where Link defeated Gannondorf in the future, but was then sent back to a time where Gannondorf wasn't defeated, resulting in that Gannondorf eventually being sent to the Twilight Realm by the Sages, instead of being sealed in the Sacred Realm like he was in the future. This results in Gannodorf returning in two completely different ways which makes two completely different timelines. And now with the new timeline having Gannon win and take the complete Triforce resulting in another huge change.
This is why Oracle of Ages doesn't make a radically different timeline while Ocarina does because Ages involves Link stopping someone from the present from messing with the past and than killing that person in the past so nothing major really happens to alter the present, except for Tree falling in love with Link and the kingdom creating a giant stone statue to honor him, two things that have minor consequences on altering the future.