Apple pay isn't on android, by definition. Unless you're talking about the competing Google Pay, which is a different competing standard.
You mean Android Pay, not Google Pay. And it's not a different, competing standard. Both Apple Pay and Android Pay use the same NFC technologies and standards.
On the name, I should point out that it's somewhat understandable that you call it "Google Pay", since Android Pay is a successor to Google Wallet, which was Google's original NFC payment solution, released in 2011 (long before Apple Pay). The Google Wallet approach was a little different, though. Because of payment network limitations, Google used a "proxy card" solution, where a Google-issued credit card was what was actually used to pay at the point of sale, and Google then charged your credit card on the backend. That approach had problems both for the user, who might not get full credit from rewards cards, and for Google, who lost money on every transaction due to the difference in fees between the card-present transaction at point of sale, and the card-not-present transaction used for user's payment, but had the supreme advantage that it would work with any credit or debit card. Banks also really disliked the proxy card solution because it threatened to take too much control of the payment systems away from them. With the intermediate routing step Google could have arranged to use any payment system on the back end, and then used its clout to get the point of sale updated to a solution that didn't involve the banks, and removed the banks from the process completely. There's no evidence Google was going to do that, but the banks were afraid of it and chose to make Google's life very hard in all sorts of ways around the NFC proxy card (and its physical, plastic analogue, which Google issued for a while).
Apple waited until networks were ready to do "network tokenization", and until some more banks were ready to handle NFC transactions, both of which are required to enable the Apple Pay model where the payment is done directly against the user's card, with payment clearinghouses routing the the transaction directly to the bank that issued the credit card. Android Pay uses this same model, with the difference that if you have a credit card which was previously used with the Google Wallet proxy card solution, Google "grandfathers" your card in and continues using the proxy. This direct model fixes the disadvantages of the proxy card solution, but means that you can only use cards whose issuers have set up the necessary infrastructure. But these days, lots of them have. In particular, the big bank service providers like First Data have got everything set up so their clients who issue credit cards can do NFC. This means that nearly all small banks and credit unions can do it, and most of the big banks can do it. Some of the big banks, and many of the medium-sized banks still aren't set up.
(Note that I've intentionally left out some details, like the first version of Google Wallet using a direct, non-tokenized approach that only worked with one bank, and some of the other intermediate steps. I figured this was long enough.)